diff --git a/lib/default/jsmn-shadinger-1.0/src/JsonGenerator.h b/lib/default/jsmn-shadinger-1.0/src/JsonGenerator.h
index 2f27b846b..1d6c0f969 100644
--- a/lib/default/jsmn-shadinger-1.0/src/JsonGenerator.h
+++ b/lib/default/jsmn-shadinger-1.0/src/JsonGenerator.h
@@ -32,7 +32,7 @@ extern String EscapeJSONString(const char *str);
 class JsonGeneratorArray {
 public:
 
-  JsonGeneratorArray(): val("[]") {}     // start with empty array
+  JsonGeneratorArray(): val(F("[]")) {}     // start with empty array
 
   void add(uint32_t uval32);
   void add(int32_t uval32);
@@ -53,7 +53,7 @@ protected:
 class JsonGeneratorObject {
 public:
 
-  JsonGeneratorObject(): val("{}") {}     // start with empty object
+  JsonGeneratorObject(): val(F("{}")) {}     // start with empty object
 
   void add(const char* key, uint32_t uval32);
   void add(const char* key, int32_t uval32);
diff --git a/tasmota/settings.ino b/tasmota/settings.ino
index b2d438df6..0ebdac4c7 100644
--- a/tasmota/settings.ino
+++ b/tasmota/settings.ino
@@ -812,10 +812,10 @@ void SettingsDefaultSet2(void)
   flag3.use_wifi_rescan |= WIFI_SCAN_REGULARLY;
   Settings.wifi_output_power = 170;
   Settings.param[P_ARP_GRATUITOUS] = WIFI_ARP_INTERVAL;
-  ParseIp(&Settings.ip_address[0], WIFI_IP_ADDRESS);
-  ParseIp(&Settings.ip_address[1], WIFI_GATEWAY);
-  ParseIp(&Settings.ip_address[2], WIFI_SUBNETMASK);
-  ParseIp(&Settings.ip_address[3], WIFI_DNS);
+  ParseIp(&Settings.ip_address[0], PSTR(WIFI_IP_ADDRESS));
+  ParseIp(&Settings.ip_address[1], PSTR(WIFI_GATEWAY));
+  ParseIp(&Settings.ip_address[2], PSTR(WIFI_SUBNETMASK));
+  ParseIp(&Settings.ip_address[3], PSTR(WIFI_DNS));
   Settings.sta_config = WIFI_CONFIG_TOOL;
 //  Settings.sta_active = 0;
   SettingsUpdateText(SET_STASSID1, PSTR(STA_SSID1));
@@ -865,22 +865,22 @@ void SettingsDefaultSet2(void)
   flag3.grouptopic_mode |= MQTT_GROUPTOPIC_FORMAT;
   SettingsUpdateText(SET_MQTT_HOST, MQTT_HOST);
   Settings.mqtt_port = MQTT_PORT;
-  SettingsUpdateText(SET_MQTT_CLIENT, MQTT_CLIENT_ID);
-  SettingsUpdateText(SET_MQTT_USER, MQTT_USER);
-  SettingsUpdateText(SET_MQTT_PWD, MQTT_PASS);
-  SettingsUpdateText(SET_MQTT_TOPIC, MQTT_TOPIC);
-  SettingsUpdateText(SET_MQTT_BUTTON_TOPIC, MQTT_BUTTON_TOPIC);
-  SettingsUpdateText(SET_MQTT_SWITCH_TOPIC, MQTT_SWITCH_TOPIC);
-  SettingsUpdateText(SET_MQTT_GRP_TOPIC, MQTT_GRPTOPIC);
-  SettingsUpdateText(SET_MQTT_FULLTOPIC, MQTT_FULLTOPIC);
+  SettingsUpdateText(SET_MQTT_CLIENT, PSTR(MQTT_CLIENT_ID));
+  SettingsUpdateText(SET_MQTT_USER, PSTR(MQTT_USER));
+  SettingsUpdateText(SET_MQTT_PWD, PSTR(MQTT_PASS));
+  SettingsUpdateText(SET_MQTT_TOPIC, PSTR(MQTT_TOPIC));
+  SettingsUpdateText(SET_MQTT_BUTTON_TOPIC, PSTR(MQTT_BUTTON_TOPIC));
+  SettingsUpdateText(SET_MQTT_SWITCH_TOPIC, PSTR(MQTT_SWITCH_TOPIC));
+  SettingsUpdateText(SET_MQTT_GRP_TOPIC, PSTR(MQTT_GRPTOPIC));
+  SettingsUpdateText(SET_MQTT_FULLTOPIC, PSTR(MQTT_FULLTOPIC));
   Settings.mqtt_retry = MQTT_RETRY_SECS;
-  SettingsUpdateText(SET_MQTTPREFIX1, SUB_PREFIX);
-  SettingsUpdateText(SET_MQTTPREFIX2, PUB_PREFIX);
-  SettingsUpdateText(SET_MQTTPREFIX3, PUB_PREFIX2);
-  SettingsUpdateText(SET_STATE_TXT1, MQTT_STATUS_OFF);
-  SettingsUpdateText(SET_STATE_TXT2, MQTT_STATUS_ON);
-  SettingsUpdateText(SET_STATE_TXT3, MQTT_CMND_TOGGLE);
-  SettingsUpdateText(SET_STATE_TXT4, MQTT_CMND_HOLD);
+  SettingsUpdateText(SET_MQTTPREFIX1, PSTR(SUB_PREFIX));
+  SettingsUpdateText(SET_MQTTPREFIX2, PSTR(PUB_PREFIX));
+  SettingsUpdateText(SET_MQTTPREFIX3, PSTR(PUB_PREFIX2));
+  SettingsUpdateText(SET_STATE_TXT1, PSTR(MQTT_STATUS_OFF));
+  SettingsUpdateText(SET_STATE_TXT2, PSTR(MQTT_STATUS_ON));
+  SettingsUpdateText(SET_STATE_TXT3, PSTR(MQTT_CMND_TOGGLE));
+  SettingsUpdateText(SET_STATE_TXT4, PSTR(MQTT_CMND_HOLD));
   memcpy_P(Settings.mqtt_fingerprint[0], default_fingerprint1, sizeof(default_fingerprint1));
   memcpy_P(Settings.mqtt_fingerprint[1], default_fingerprint2, sizeof(default_fingerprint2));
   Settings.tele_period = TELE_PERIOD;
diff --git a/tasmota/support.ino b/tasmota/support.ino
index 0d5ce5b94..dace03c58 100644
--- a/tasmota/support.ino
+++ b/tasmota/support.ino
@@ -384,7 +384,7 @@ char* Uint64toHex(uint64_t value, char *str, uint16_t bits)
 char* dtostrfd(double number, unsigned char prec, char *s)
 {
   if ((isnan(number)) || (isinf(number))) {  // Fix for JSON output (https://stackoverflow.com/questions/1423081/json-left-out-infinity-and-nan-json-status-in-ecmascript)
-    strcpy(s, "null");
+    strcpy_P(s, PSTR("null"));
     return s;
   } else {
     return dtostrf(number, 1, prec, s);
@@ -661,10 +661,13 @@ bool ValidIpAddress(const char* str)
   return (*p == '\0');
 }
 
-bool ParseIp(uint32_t* addr, const char* str)
+bool ParseIp(uint32_t* addr, const char* str_p)
 {
   uint8_t *part = (uint8_t*)addr;
   uint8_t i;
+  char str_r[strlen_P(str_p)+1];
+  char * str = &str_r[0];
+  strcpy_P(str, str_p);
 
   *addr = 0;
   for (i = 0; i < 4; i++) {
@@ -861,7 +864,7 @@ float ConvertPressureForSeaLevel(float pressure)
 
 String PressureUnit(void)
 {
-  return (Settings.flag.pressure_conversion) ? String(D_UNIT_MILLIMETER_MERCURY) : String(D_UNIT_PRESSURE);
+  return (Settings.flag.pressure_conversion) ? String(F(D_UNIT_MILLIMETER_MERCURY)) : String(F(D_UNIT_PRESSURE));
 }
 
 float ConvertSpeed(float s)
@@ -1024,11 +1027,11 @@ String GetSerialConfig(void) {
   // b00000x00 - 1 or 2 stop bits
   // b000xx000 - None, Even or Odd parity
 
-  const char kParity[] = "NEOI";
+  const static char kParity[] PROGMEM = "NEOI";
 
   char config[4];
   config[0] = '5' + (Settings.serial_config & 0x3);
-  config[1] = kParity[(Settings.serial_config >> 3) & 0x3];
+  config[1] = pgm_read_byte(&kParity[(Settings.serial_config >> 3) & 0x3]);
   config[2] = '1' + ((Settings.serial_config >> 2) & 0x1);
   config[3] = '\0';
   return String(config);
diff --git a/tasmota/support_command.ino b/tasmota/support_command.ino
index 1c5e32474..145d86ef2 100644
--- a/tasmota/support_command.ino
+++ b/tasmota/support_command.ino
@@ -110,7 +110,7 @@ void ResponseCmndStateText(uint32_t value)
 
 void ResponseCmndDone(void)
 {
-  ResponseCmndChar(D_JSON_DONE);
+  ResponseCmndChar(PSTR(D_JSON_DONE));
 }
 
 void ResponseCmndIdxChar(const char* value)
@@ -352,7 +352,7 @@ void CmndBacklog(void)
 #else
     TasmotaGlobal.backlog_pointer = TasmotaGlobal.backlog_index;
 #endif
-    ResponseCmndChar(blflag ? D_JSON_EMPTY : D_JSON_ABORTED);
+    ResponseCmndChar(blflag ? PSTR(D_JSON_EMPTY) : PSTR(D_JSON_ABORTED));
   }
 }
 
@@ -1282,7 +1282,7 @@ void CmndTemplate(void)
       if (Settings.module != USER_MODULE) {
         ModuleDefault(Settings.module);
       }
-      SettingsUpdateText(SET_TEMPLATE_NAME, "Merged");
+      SettingsUpdateText(SET_TEMPLATE_NAME, PSTR("Merged"));
       uint32_t j = 0;
       for (uint32_t i = 0; i < ARRAY_SIZE(Settings.user_template.gp.io); i++) {
         if (6 == i) { j = 9; }
diff --git a/tasmota/support_network.ino b/tasmota/support_network.ino
index b2bb73bf0..e2b24d782 100644
--- a/tasmota/support_network.ino
+++ b/tasmota/support_network.ino
@@ -38,7 +38,7 @@ void StartMdns(void) {
 //        mdns_delayed_start = Settings.param[P_MDNS_DELAYED_START];
         MDNS.end(); // close existing or MDNS.begin will fail
         Mdns.begun = (uint8_t)MDNS.begin(TasmotaGlobal.hostname);
-        AddLog_P(LOG_LEVEL_INFO, PSTR(D_LOG_MDNS "%s"), (Mdns.begun) ? D_INITIALIZED : D_FAILED);
+        AddLog_P(LOG_LEVEL_INFO, PSTR(D_LOG_MDNS "%s"), (Mdns.begun) ? PSTR(D_INITIALIZED) : PSTR(D_FAILED));
 //      }
     }
   }
diff --git a/tasmota/support_rtc.ino b/tasmota/support_rtc.ino
index 08f7cfc3d..2f2403e7a 100644
--- a/tasmota/support_rtc.ino
+++ b/tasmota/support_rtc.ino
@@ -33,8 +33,8 @@ const uint32_t MINS_PER_HOUR = 60UL;
 
 Ticker TickerRtc;
 
-static const uint8_t kDaysInMonth[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }; // API starts months from 1, this array starts from 0
-static const char kMonthNamesEnglish[] = "JanFebMarAprMayJunJulAugSepOctNovDec";
+static const uint8_t kDaysInMonth[] PROGMEM = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }; // API starts months from 1, this array starts from 0
+static const char kMonthNamesEnglish[] PROGMEM = "JanFebMarAprMayJunJulAugSepOctNovDec";
 
 struct RTC {
   uint32_t utc_time = 0;
@@ -88,7 +88,9 @@ String GetBuildDateAndTime(void)
   // "2017-03-07T11:08:02" - ISO8601:2004
   char bdt[21];
   char *p;
-  char mdate[] = __DATE__;  // "Mar  7 2017"
+  static const char mdate_P[] PROGMEM = __DATE__;  // "Mar  7 2017"
+  char mdate[strlen_P(mdate_P)+1];      // copy on stack first
+  strcpy_P(mdate, mdate_P);
   char *smonth = mdate;
   int day = 0;
   int year = 0;
@@ -107,8 +109,10 @@ String GetBuildDateAndTime(void)
       year = atoi(str);
     }
   }
-  int month = (strstr(kMonthNamesEnglish, smonth) -kMonthNamesEnglish) /3 +1;
-  snprintf_P(bdt, sizeof(bdt), PSTR("%d" D_YEAR_MONTH_SEPARATOR "%02d" D_MONTH_DAY_SEPARATOR "%02d" D_DATE_TIME_SEPARATOR "%s"), year, month, day, __TIME__);
+  char MonthNamesEnglish[sizeof(kMonthNamesEnglish)];
+  strcpy_P(MonthNamesEnglish, kMonthNamesEnglish);
+  int month = (strstr(MonthNamesEnglish, smonth) -MonthNamesEnglish) /3 +1;
+  snprintf_P(bdt, sizeof(bdt), PSTR("%d" D_YEAR_MONTH_SEPARATOR "%02d" D_MONTH_DAY_SEPARATOR "%02d" D_DATE_TIME_SEPARATOR "%s"), year, month, day, PSTR(__TIME__));
   return String(bdt);  // 2017-03-07T11:08:02
 }
 
@@ -290,7 +294,7 @@ void BreakTime(uint32_t time_input, TIME_T &tm)
         month_length = 28;
       }
     } else {
-      month_length = kDaysInMonth[month];
+      month_length = pgm_read_byte(&kDaysInMonth[month]);
     }
 
     if (time >= month_length) {
@@ -326,7 +330,7 @@ uint32_t MakeTime(TIME_T &tm)
     if ((2 == i) && LEAP_YEAR(tm.year)) {
       seconds += SECS_PER_DAY * 29;
     } else {
-      seconds += SECS_PER_DAY * kDaysInMonth[i-1];  // monthDay array starts from 0
+      seconds += SECS_PER_DAY * pgm_read_byte(&kDaysInMonth[i-1]);  // monthDay array starts from 0
     }
   }
   seconds+= (tm.day_of_month - 1) * SECS_PER_DAY;
diff --git a/tasmota/support_tasmota.ino b/tasmota/support_tasmota.ino
index 64bc6e09d..40d5836ad 100644
--- a/tasmota/support_tasmota.ino
+++ b/tasmota/support_tasmota.ino
@@ -20,10 +20,12 @@
 const char kSleepMode[] PROGMEM = "Dynamic|Normal";
 const char kPrefixes[] PROGMEM = D_CMND "|" D_STAT "|" D_TELE;
 
-char* Format(char* output, const char* input, int size)
+char* Format(char* output, const char* input_p, int size)
 {
   char *token;
   uint32_t digits = 0;
+  char input[strlen_P(input_p)+1];  // copy from PMEM to RAM
+  strcpy_P(input, input_p);
 
   if (strchr(input, '%') != nullptr) {
     strlcpy(output, input, size);
@@ -102,7 +104,7 @@ char* GetTopic_P(char *stopic, uint32_t prefix, char *topic, const char* subtopi
       fulltopic += TasmotaGlobal.mqtt_client;
       fulltopic += F("_fb");                  // cmnd/<mqttclient>_fb
     } else {
-      fulltopic += topic;                     // cmnd/<grouptopic>
+      fulltopic += (const __FlashStringHelper *)topic;                     // cmnd/<grouptopic>
     }
   } else {
     fulltopic = SettingsText(SET_MQTT_FULLTOPIC);
@@ -118,7 +120,7 @@ char* GetTopic_P(char *stopic, uint32_t prefix, char *topic, const char* subtopi
     }
     fulltopic.replace(FPSTR(MQTT_TOKEN_PREFIX), SettingsText(SET_MQTTPREFIX1 + prefix));
 
-    fulltopic.replace(FPSTR(MQTT_TOKEN_TOPIC), topic);
+    fulltopic.replace(FPSTR(MQTT_TOKEN_TOPIC), (const __FlashStringHelper *)topic);
     fulltopic.replace(F("%hostname%"), TasmotaGlobal.hostname);
     String token_id = WiFi.macAddress();
     token_id.replace(":", "");
@@ -486,7 +488,7 @@ bool SendKey(uint32_t key, uint32_t device, uint32_t state)
 #endif  // USE_DOMOTICZ
     result = !Settings.flag3.button_switch_force_local;  // SetOption61 - Force local operation when button/switch topic is set
   } else {
-    Response_P(PSTR("{\"%s%d\":{\"State\":%d}}"), (key) ? "Switch" : "Button", device, state);
+    Response_P(PSTR("{\"%s%d\":{\"State\":%d}}"), (key) ? PSTR("Switch") : PSTR("Button"), device, state);
     result = XdrvRulesProcess();
   }
 #ifdef USE_PWM_DIMMER
@@ -742,7 +744,8 @@ void TempHumDewShow(bool json, bool pass_on, const char *types, float f_temperat
 String GetSwitchText(uint32_t i) {
   String switch_text = SettingsText(SET_SWITCH_TXT1 + i);
   if ('\0' == switch_text[0]) {
-    switch_text = D_JSON_SWITCH + String(i +1);
+    switch_text = F(D_JSON_SWITCH);
+    switch_text += String(i+1);
   }
   return switch_text;
 }
diff --git a/tasmota/support_wifi.ino b/tasmota/support_wifi.ino
index 15f5e10c2..68208b941 100644
--- a/tasmota/support_wifi.ino
+++ b/tasmota/support_wifi.ino
@@ -176,7 +176,7 @@ void WiFiSetSleepMode(void)
 
 void WifiBegin(uint8_t flag, uint8_t channel)
 {
-  const char kWifiPhyMode[] = " bgnl";
+  const static char kWifiPhyMode[] PROGMEM = " bgnl";
 
 #ifdef USE_EMULATION
   UdpDisconnect();
@@ -218,7 +218,7 @@ void WifiBegin(uint8_t flag, uint8_t channel)
     WiFi.begin(SettingsText(SET_STASSID1 + Settings.sta_active), SettingsText(SET_STAPWD1 + Settings.sta_active));
   }
   AddLog_P(LOG_LEVEL_INFO, PSTR(D_LOG_WIFI D_CONNECTING_TO_AP "%d %s%s " D_IN_MODE " 11%c " D_AS " %s..."),
-    Settings.sta_active +1, SettingsText(SET_STASSID1 + Settings.sta_active), stemp, kWifiPhyMode[WiFi.getPhyMode() & 0x3], TasmotaGlobal.hostname);
+    Settings.sta_active +1, SettingsText(SET_STASSID1 + Settings.sta_active), stemp, pgm_read_byte(&kWifiPhyMode[WiFi.getPhyMode() & 0x3]), TasmotaGlobal.hostname);
 
 #if LWIP_IPV6
   for (bool configured = false; !configured;) {
diff --git a/tasmota/tasmota.ino b/tasmota/tasmota.ino
index 2407e61b1..18995cd47 100644
--- a/tasmota/tasmota.ino
+++ b/tasmota/tasmota.ino
@@ -302,7 +302,7 @@ void setup(void) {
     snprintf_P(TasmotaGlobal.version, sizeof(TasmotaGlobal.version), PSTR("%s.%d"), TasmotaGlobal.version, VERSION & 0xff);
   }
   // Thehackbox inserts "release" or "commit number" before compiling using sed -i -e 's/PSTR("(%s)")/PSTR("(85cff52-%s)")/g' tasmota.ino
-  snprintf_P(TasmotaGlobal.image_name, sizeof(TasmotaGlobal.image_name), PSTR("(%s)"), CODE_IMAGE_STR);  // Results in (85cff52-tasmota) or (release-tasmota)
+  snprintf_P(TasmotaGlobal.image_name, sizeof(TasmotaGlobal.image_name), PSTR("(%s)"), PSTR(CODE_IMAGE_STR));  // Results in (85cff52-tasmota) or (release-tasmota)
 
   Format(TasmotaGlobal.mqtt_client, SettingsText(SET_MQTT_CLIENT), sizeof(TasmotaGlobal.mqtt_client));
   Format(TasmotaGlobal.mqtt_topic, SettingsText(SET_MQTT_TOPIC), sizeof(TasmotaGlobal.mqtt_topic));
@@ -321,7 +321,7 @@ void setup(void) {
   SetPowerOnState();
 
   AddLog_P(LOG_LEVEL_INFO, PSTR(D_PROJECT " %s %s " D_VERSION " %s%s-" ARDUINO_CORE_RELEASE "(%s)"),
-    PROJECT, SettingsText(SET_DEVICENAME), TasmotaGlobal.version, TasmotaGlobal.image_name, GetBuildDateAndTime().c_str());
+    PSTR(PROJECT), SettingsText(SET_DEVICENAME), TasmotaGlobal.version, TasmotaGlobal.image_name, GetBuildDateAndTime().c_str());
 #ifdef FIRMWARE_MINIMAL
   AddLog_P(LOG_LEVEL_INFO, PSTR(D_WARNING_MINIMAL_VERSION));
 #endif  // FIRMWARE_MINIMAL
diff --git a/tasmota/xdrv_01_webserver.ino b/tasmota/xdrv_01_webserver.ino
index 42cbf1af4..b43bc573f 100644
--- a/tasmota/xdrv_01_webserver.ino
+++ b/tasmota/xdrv_01_webserver.ino
@@ -376,9 +376,10 @@ struct WEB {
 } Web;
 
 // Helper function to avoid code duplication (saves 4k Flash)
+// arg can be in PROGMEM
 static void WebGetArg(const char* arg, char* out, size_t max)
 {
-  String s = Webserver->arg(arg);
+  String s = Webserver->arg((const __FlashStringHelper *)arg);
   strlcpy(out, s.c_str(), max);
 //  out[max-1] = '\0';  // Ensure terminating NUL
 }
@@ -460,7 +461,7 @@ void StartWebserver(int type, IPAddress ipweb)
         WebServer_on(uri, line.handler, pgm_read_byte(&line.method));
       }
       Webserver->onNotFound(HandleNotFound);
-      Webserver->on("/u2", HTTP_POST, HandleUploadDone, HandleUploadLoop);  // this call requires 2 functions so we keep a direct call
+      Webserver->on(F("/u2"), HTTP_POST, HandleUploadDone, HandleUploadLoop);  // this call requires 2 functions so we keep a direct call
 #ifndef FIRMWARE_MINIMAL
       XdrvCall(FUNC_WEB_ADD_HANDLER);
       XsnsCall(FUNC_WEB_ADD_HANDLER);
@@ -691,7 +692,7 @@ void WSContentStart_P(const char* title, bool auth)
   WSContentBegin(200, CT_HTML);
 
   if (title != nullptr) {
-    WSContentSend_P(HTTP_HEADER1, D_HTML_LANGUAGE, SettingsText(SET_DEVICENAME), title);
+    WSContentSend_P(HTTP_HEADER1, PSTR(D_HTML_LANGUAGE), SettingsText(SET_DEVICENAME), title);
   }
 }
 
@@ -767,7 +768,7 @@ void WSContentButton(uint32_t title_index)
     WSContentSend_P(PSTR("<p><form action='%s' method='get' onsubmit='return confirm(\"%s\");'><button name='%s' class='button bred'>%s</button></form></p>"),
       GetTextIndexed(action, sizeof(action), title_index, kButtonAction),
       GetTextIndexed(confirm, sizeof(confirm), title_index, kButtonConfirm),
-      (!title_index) ? "rst" : "non",
+      (!title_index) ? PSTR("rst") : PSTR("non"),
       GetTextIndexed(title, sizeof(title), title_index, kButtonTitle));
   } else {
     WSContentSend_P(PSTR("<p><form action='%s' method='get'><button>%s</button></form></p>"),
@@ -866,8 +867,8 @@ void HandleWifiLogin(void)
 void WebSliderColdWarm(void)
 {
   WSContentSend_P(HTTP_MSG_SLIDER_GRADIENT,  // Cold Warm
-    "a",             // a - Unique HTML id
-    "#eff", "#f81",  // 6500k in RGB (White) to 2500k in RGB (Warm Yellow)
+    PSTR("a"),             // a - Unique HTML id
+    PSTR("#eff"), PSTR("#f81"),  // 6500k in RGB (White) to 2500k in RGB (Warm Yellow)
     1,               // sl1
     153, 500,        // Range color temperature
     LightGetColorTemp(),
@@ -879,17 +880,17 @@ void HandleRoot(void)
 {
   if (CaptivePortal()) { return; }  // If captive portal redirect instead of displaying the page.
 
-  if (Webserver->hasArg("rst")) {
+  if (Webserver->hasArg(F("rst"))) {
     WebRestart(0);
     return;
   }
 
   if (WifiIsInManagerMode()) {
 #ifndef FIRMWARE_MINIMAL
-    if (strlen(SettingsText(SET_WEBPWD)) && !(Webserver->hasArg("USER1")) && !(Webserver->hasArg("PASS1")) && HTTP_MANAGER_RESET_ONLY != Web.state) {
+    if (strlen(SettingsText(SET_WEBPWD)) && !(Webserver->hasArg(F("USER1"))) && !(Webserver->hasArg(F("PASS1"))) && HTTP_MANAGER_RESET_ONLY != Web.state) {
       HandleWifiLogin();
     } else {
-      if (!strlen(SettingsText(SET_WEBPWD)) || (((Webserver->arg("USER1") == WEB_USERNAME ) && (Webserver->arg("PASS1") == SettingsText(SET_WEBPWD) )) || HTTP_MANAGER_RESET_ONLY == Web.state)) {
+      if (!strlen(SettingsText(SET_WEBPWD)) || (((Webserver->arg(F("USER1")) == WEB_USERNAME ) && (Webserver->arg(F("PASS1")) == SettingsText(SET_WEBPWD) )) || HTTP_MANAGER_RESET_ONLY == Web.state)) {
         HandleWifiConfiguration();
       } else {
         // wrong user and pass
@@ -936,8 +937,8 @@ void HandleRoot(void)
           LightGetHSB(&hue, &sat, nullptr);
 
           WSContentSend_P(HTTP_MSG_SLIDER_GRADIENT,  // Hue
-            "b",             // b - Unique HTML id
-            "#800", PSTR("#f00 5%,#ff0 20%,#0f0 35%,#0ff 50%,#00f 65%,#f0f 80%,#f00 95%,#800"),  // Hue colors
+            PSTR("b"),             // b - Unique HTML id
+            PSTR("#800"), PSTR("#f00 5%,#ff0 20%,#0f0 35%,#0ff 50%,#00f 65%,#f0f 80%,#f00 95%,#800"),  // Hue colors
             2,               // sl2 - Unique range HTML id - Used as source for Saturation end color
             1, 359,          // Range valid Hue
             hue,
@@ -951,7 +952,7 @@ void HandleRoot(void)
           snprintf_P(stemp, sizeof(stemp), PSTR("#%02X%02X%02X"), red, green, blue);  // Saturation end color
 
           WSContentSend_P(HTTP_MSG_SLIDER_GRADIENT,  // Saturation
-            "s",             // s - Unique HTML id related to eb('s').style.background='linear-gradient(to right,rgb('+sl+'%%,'+sl+'%%,'+sl+'%%),hsl('+eb('sl2').value+',100%%,50%%))';
+            PSTR("s"),             // s - Unique HTML id related to eb('s').style.background='linear-gradient(to right,rgb('+sl+'%%,'+sl+'%%,'+sl+'%%),hsl('+eb('sl2').value+',100%%,50%%))';
             scolor, stemp,   // Brightness to max current color
             3,               // sl3 - Unique range HTML id - Not used
             0, 100,          // Range 0 to 100%
@@ -960,8 +961,8 @@ void HandleRoot(void)
         }
 
         WSContentSend_P(HTTP_MSG_SLIDER_GRADIENT,  // Brightness - Black to White
-          "c",               // c - Unique HTML id
-          "#000", "#fff",    // Black to White
+          PSTR("c"),               // c - Unique HTML id
+          PSTR("#000"), PSTR("#fff"),    // Black to White
           4,                 // sl4 - Unique range HTML id - Used as source for Saturation begin color
           Settings.flag3.slider_dimmer_stay_on, 100,  // Range 0/1 to 100% (SetOption77 - Do not power off if slider moved to far left)
           Settings.light_dimmer,
@@ -972,8 +973,8 @@ void HandleRoot(void)
             WebSliderColdWarm();
           }
           WSContentSend_P(HTTP_MSG_SLIDER_GRADIENT,  // White brightness - Black to White
-            "f",             // f - Unique HTML id
-            "#000", "#fff",  // Black to White
+            PSTR("f"),             // f - Unique HTML id
+            PSTR("#000"), PSTR("#fff"),  // Black to White
             5,               // sl5 - Unique range HTML id - Not used
             Settings.flag3.slider_dimmer_stay_on, 100,  // Range 0/1 to 100% (SetOption77 - Do not power off if slider moved to far left)
             LightGetDimmer(2),
@@ -987,7 +988,7 @@ void HandleRoot(void)
 
           WSContentSend_P(HTTP_MSG_SLIDER_GRADIENT,  // Channel brightness - Black to White
             stemp,           // e1 to e5 - Unique HTML id
-            "#000", "#fff",  // Black to White
+            PSTR("#000"), PSTR("#fff"),  // Black to White
             i+1,             // sl1 to sl5 - Unique range HTML id - Not used
             1, 100,          // Range 1 to 100%
             changeUIntScale(Settings.light_color[i], 0, 255, 0, 100),
@@ -1008,7 +1009,7 @@ void HandleRoot(void)
 #ifdef USE_SONOFF_IFAN
     if (IsModuleIfan()) {
       WSContentSend_P(HTTP_DEVICE_CONTROL, 36, 1,
-        (strlen(SettingsText(SET_BUTTON1))) ? SettingsText(SET_BUTTON1) : D_BUTTON_TOGGLE,
+        (strlen(SettingsText(SET_BUTTON1))) ? SettingsText(SET_BUTTON1) : PSTR(D_BUTTON_TOGGLE),
         "");
       for (uint32_t i = 0; i < MaxFanspeed(); i++) {
         snprintf_P(stemp, sizeof(stemp), PSTR("%d"), i);
@@ -1031,7 +1032,7 @@ void HandleRoot(void)
 #endif  // USE_SHUTTER
         snprintf_P(stemp, sizeof(stemp), PSTR(" %d"), idx);
         WSContentSend_P(HTTP_DEVICE_CONTROL, 100 / TasmotaGlobal.devices_present, idx,
-          (set_button) ? SettingsText(SET_BUTTON1 + idx -1) : (TasmotaGlobal.devices_present < 5) ? D_BUTTON_TOGGLE : "",
+          (set_button) ? SettingsText(SET_BUTTON1 + idx -1) : (TasmotaGlobal.devices_present < 5) ? PSTR(D_BUTTON_TOGGLE) : "",
           (set_button) ? "" : (TasmotaGlobal.devices_present > 1) ? stemp : "");
       }
 #ifdef USE_SONOFF_IFAN
@@ -1107,7 +1108,7 @@ bool HandleRootStatusRefresh(void)
   char svalue[32];                   // Command and number parameter
   char webindex[5];                  // WebGetArg name
 
-  WebGetArg("o", tmp, sizeof(tmp));  // 1 - 16 Device number for button Toggle or Fanspeed
+  WebGetArg(PSTR("o"), tmp, sizeof(tmp));  // 1 - 16 Device number for button Toggle or Fanspeed
   if (strlen(tmp)) {
     ShowWebSource(SRC_WEBGUI);
     uint32_t device = atoi(tmp);
@@ -1153,12 +1154,12 @@ bool HandleRootStatusRefresh(void)
 #endif  // USE_TUYA_MCU
   }
 #ifdef USE_LIGHT
-  WebGetArg("d0", tmp, sizeof(tmp));  // 0 - 100 Dimmer value
+  WebGetArg(PSTR("d0"), tmp, sizeof(tmp));  // 0 - 100 Dimmer value
   if (strlen(tmp)) {
     snprintf_P(svalue, sizeof(svalue), PSTR(D_CMND_DIMMER " %s"), tmp);
     ExecuteWebCommand(svalue, SRC_WEBGUI);
   }
-  WebGetArg("w0", tmp, sizeof(tmp));  // 0 - 100 White value
+  WebGetArg(PSTR("w0"), tmp, sizeof(tmp));  // 0 - 100 White value
   if (strlen(tmp)) {
     snprintf_P(svalue, sizeof(svalue), PSTR(D_CMND_WHITE " %s"), tmp);
     ExecuteWebCommand(svalue, SRC_WEBGUI);
@@ -1173,17 +1174,17 @@ bool HandleRootStatusRefresh(void)
       ExecuteWebCommand(svalue, SRC_WEBGUI);
     }
   }
-  WebGetArg("t0", tmp, sizeof(tmp));  // 153 - 500 Color temperature
+  WebGetArg(PSTR("t0"), tmp, sizeof(tmp));  // 153 - 500 Color temperature
   if (strlen(tmp)) {
     snprintf_P(svalue, sizeof(svalue), PSTR(D_CMND_COLORTEMPERATURE " %s"), tmp);
     ExecuteWebCommand(svalue, SRC_WEBGUI);
   }
-  WebGetArg("h0", tmp, sizeof(tmp));  // 0 - 359 Hue value
+  WebGetArg(PSTR("h0"), tmp, sizeof(tmp));  // 0 - 359 Hue value
   if (strlen(tmp)) {
     snprintf_P(svalue, sizeof(svalue), PSTR(D_CMND_HSBCOLOR  "1 %s"), tmp);
     ExecuteWebCommand(svalue, SRC_WEBGUI);
   }
-  WebGetArg("n0", tmp, sizeof(tmp));  // 0 - 99 Saturation value
+  WebGetArg(PSTR("n0"), tmp, sizeof(tmp));  // 0 - 99 Saturation value
   if (strlen(tmp)) {
     snprintf_P(svalue, sizeof(svalue), PSTR(D_CMND_HSBCOLOR  "2 %s"), tmp);
     ExecuteWebCommand(svalue, SRC_WEBGUI);
@@ -1200,19 +1201,19 @@ bool HandleRootStatusRefresh(void)
   }
 #endif  // USE_SHUTTER
 #ifdef USE_SONOFF_RF
-  WebGetArg("k", tmp, sizeof(tmp));  // 1 - 16 Pre defined RF keys
+  WebGetArg(PSTR("k"), tmp, sizeof(tmp));  // 1 - 16 Pre defined RF keys
   if (strlen(tmp)) {
     snprintf_P(svalue, sizeof(svalue), PSTR(D_CMND_RFKEY "%s"), tmp);
     ExecuteWebCommand(svalue, SRC_WEBGUI);
   }
 #endif  // USE_SONOFF_RF
 #ifdef USE_ZIGBEE
-  WebGetArg("zbj", tmp, sizeof(tmp));
+  WebGetArg(PSTR("zbj"), tmp, sizeof(tmp));
   if (strlen(tmp)) {
     snprintf_P(svalue, sizeof(svalue), PSTR("ZbPermitJoin"));
     ExecuteWebCommand(svalue, SRC_WEBGUI);
   }
-  WebGetArg("zbr", tmp, sizeof(tmp));
+  WebGetArg(PSTR("zbr"), tmp, sizeof(tmp));
   if (strlen(tmp)) {
     snprintf_P(svalue, sizeof(svalue), PSTR("ZbMap"));
     ExecuteWebCommand(svalue, SRC_WEBGUI);
@@ -1315,7 +1316,7 @@ void WSContentSendNiceLists(uint32_t option) {
   char stemp[30];                                             // Template number and Sensor name
   for (uint32_t i = 0; i < ARRAY_SIZE(kGpioNiceList); i++) {  // GPIO: }2'0'>None (0)}3}2'17'>Button1 (17)}3...
     if (option && (1 == i)) {
-      WSContentSend_P(HTTP_MODULE_TEMPLATE_REPLACE_NO_INDEX, AGPIO(GPIO_USER), D_SENSOR_USER);  // }2'255'>User}3
+      WSContentSend_P(HTTP_MODULE_TEMPLATE_REPLACE_NO_INDEX, AGPIO(GPIO_USER), PSTR(D_SENSOR_USER));  // }2'255'>User}3
     }
     uint32_t ridx = pgm_read_word(kGpioNiceList + i) & 0xFFE0;
     uint32_t midx = BGPIO(ridx);
@@ -1356,7 +1357,7 @@ void WSContentSendAdcNiceList(uint32_t option) {
   WSContentSend_P(PSTR("os=\""));
   for (uint32_t i = 0; i < ARRAY_SIZE(kAdcNiceList); i++) {   // GPIO: }2'0'>None}3}2'17'>Analog}3...
     if (option && (1 == i)) {
-      WSContentSend_P(HTTP_MODULE_TEMPLATE_REPLACE_NO_INDEX, AGPIO(GPIO_USER), D_SENSOR_USER);  // }2'15'>User}3
+      WSContentSend_P(HTTP_MODULE_TEMPLATE_REPLACE_NO_INDEX, AGPIO(GPIO_USER), PSTR(D_SENSOR_USER));  // }2'15'>User}3
     }
     uint32_t ridx = pgm_read_word(kAdcNiceList + i) & 0xFFE0;
     uint32_t midx = BGPIO(ridx);
@@ -1372,7 +1373,7 @@ void HandleTemplateConfiguration(void)
 {
   if (!HttpCheckPriviledgedAccess()) { return; }
 
-  if (Webserver->hasArg("save")) {
+  if (Webserver->hasArg(F("save"))) {
     TemplateSaveSettings();
     WebRestart(1);
     return;
@@ -1380,7 +1381,7 @@ void HandleTemplateConfiguration(void)
 
   char stemp[30];                                           // Template number and Sensor name
 
-  WebGetArg("t", stemp, sizeof(stemp));                     // 0 - 69 Template number
+  WebGetArg(PSTR("t"), stemp, sizeof(stemp));                     // 0 - 69 Template number
   if (strlen(stemp)) {
     uint32_t module = atoi(stemp);
     uint32_t module_save = Settings.module;
@@ -1474,7 +1475,7 @@ void TemplateSaveSettings(void)
   char tmp[TOPSZ];                                          // WebGetArg NAME and GPIO/BASE/FLAG byte value
   char svalue[300];                                         // Template command string
 
-  WebGetArg("s1", tmp, sizeof(tmp));                        // NAME
+  WebGetArg(PSTR("s1"), tmp, sizeof(tmp));                        // NAME
   snprintf_P(svalue, sizeof(svalue), PSTR(D_CMND_TEMPLATE " {\"" D_JSON_NAME "\":\"%s\",\"" D_JSON_GPIO "\":["), tmp);
 
   uint32_t j = 0;
@@ -1492,7 +1493,7 @@ void TemplateSaveSettings(void)
     uint32_t state = Webserver->hasArg(webindex) << i;      // FLAG
     flag += state;
   }
-  WebGetArg("g99", tmp, sizeof(tmp));                       // BASE
+  WebGetArg(PSTR("g99"), tmp, sizeof(tmp));                       // BASE
   uint32_t base = atoi(tmp) +1;
 
   snprintf_P(svalue, sizeof(svalue), PSTR("%s],\"" D_JSON_FLAG "\":%d,\"" D_JSON_BASE "\":%d}"), svalue, flag, base);
@@ -1505,7 +1506,7 @@ void HandleModuleConfiguration(void)
 {
   if (!HttpCheckPriviledgedAccess()) { return; }
 
-  if (Webserver->hasArg("save")) {
+  if (Webserver->hasArg(F("save"))) {
     ModuleSaveSettings();
     WebRestart(1);
     return;
@@ -1572,7 +1573,7 @@ void ModuleSaveSettings(void)
 {
   char tmp[8];         // WebGetArg numbers only
 
-  WebGetArg("g99", tmp, sizeof(tmp));
+  WebGetArg(PSTR("g99"), tmp, sizeof(tmp));
   uint32_t new_module = (!strlen(tmp)) ? MODULE : atoi(tmp);
   Settings.last_module = Settings.module;
   Settings.module = new_module;
@@ -1624,7 +1625,7 @@ void HandleWifiConfiguration(void)
 
   AddLog_P(LOG_LEVEL_DEBUG, PSTR(D_LOG_HTTP D_CONFIGURE_WIFI));
 
-  if (Webserver->hasArg("save") && HTTP_MANAGER_RESET_ONLY != Web.state) {
+  if (Webserver->hasArg(F("save")) && HTTP_MANAGER_RESET_ONLY != Web.state) {
     WifiSaveSettings();
     WebRestart(2);
     return;
@@ -1639,7 +1640,7 @@ void HandleWifiConfiguration(void)
 #endif  // USE_ENHANCED_GUI_WIFI_SCAN
 
   if (HTTP_MANAGER_RESET_ONLY != Web.state) {
-    if (Webserver->hasArg("scan")) {
+    if (Webserver->hasArg(F("scan"))) {
 #ifdef USE_EMULATION
       UdpDisconnect();
 #endif  // USE_EMULATION
@@ -1776,20 +1777,20 @@ void WifiSaveSettings(void)
 {
   char tmp[TOPSZ];  // Max length is currently 150
 
-  WebGetArg("h", tmp, sizeof(tmp));
+  WebGetArg(PSTR("h"), tmp, sizeof(tmp));
   SettingsUpdateText(SET_HOSTNAME, (!strlen(tmp)) ? WIFI_HOSTNAME : tmp);
   if (strchr(SettingsText(SET_HOSTNAME), '%') != nullptr) {
     SettingsUpdateText(SET_HOSTNAME, WIFI_HOSTNAME);
   }
-  WebGetArg("c", tmp, sizeof(tmp));
+  WebGetArg(PSTR("c"), tmp, sizeof(tmp));
   SettingsUpdateText(SET_CORS, (!strlen(tmp)) ? CORS_DOMAIN : tmp);
-  WebGetArg("s1", tmp, sizeof(tmp));
+  WebGetArg(PSTR("s1"), tmp, sizeof(tmp));
   SettingsUpdateText(SET_STASSID1, (!strlen(tmp)) ? STA_SSID1 : tmp);
-  WebGetArg("s2", tmp, sizeof(tmp));
+  WebGetArg(PSTR("s2"), tmp, sizeof(tmp));
   SettingsUpdateText(SET_STASSID2, (!strlen(tmp)) ? STA_SSID2 : tmp);
-  WebGetArg("p1", tmp, sizeof(tmp));
+  WebGetArg(PSTR("p1"), tmp, sizeof(tmp));
   SettingsUpdateText(SET_STAPWD1, (!strlen(tmp)) ? "" : (strlen(tmp) < 5) ? SettingsText(SET_STAPWD1) : tmp);
-  WebGetArg("p2", tmp, sizeof(tmp));
+  WebGetArg(PSTR("p2"), tmp, sizeof(tmp));
   SettingsUpdateText(SET_STAPWD2, (!strlen(tmp)) ? "" : (strlen(tmp) < 5) ? SettingsText(SET_STAPWD2) : tmp);
   AddLog_P(LOG_LEVEL_INFO, PSTR(D_LOG_WIFI D_CMND_HOSTNAME " %s, " D_CMND_SSID "1 %s, " D_CMND_SSID "2 %s, " D_CMND_CORS " %s"),
     SettingsText(SET_HOSTNAME), SettingsText(SET_STASSID1), SettingsText(SET_STASSID2), SettingsText(SET_CORS));
@@ -1839,19 +1840,19 @@ void LoggingSaveSettings(void)
 {
   char tmp[TOPSZ];  // Max length is currently 33
 
-  WebGetArg("l0", tmp, sizeof(tmp));
+  WebGetArg(PSTR("l0"), tmp, sizeof(tmp));
   SetSeriallog((!strlen(tmp)) ? SERIAL_LOG_LEVEL : atoi(tmp));
-  WebGetArg("l1", tmp, sizeof(tmp));
+  WebGetArg(PSTR("l1"), tmp, sizeof(tmp));
   Settings.weblog_level = (!strlen(tmp)) ? WEB_LOG_LEVEL : atoi(tmp);
-  WebGetArg("l2", tmp, sizeof(tmp));
+  WebGetArg(PSTR("l2"), tmp, sizeof(tmp));
   Settings.mqttlog_level = (!strlen(tmp)) ? MQTT_LOG_LEVEL : atoi(tmp);
-  WebGetArg("l3", tmp, sizeof(tmp));
+  WebGetArg(PSTR("l3"), tmp, sizeof(tmp));
   SetSyslog((!strlen(tmp)) ? SYS_LOG_LEVEL : atoi(tmp));
-  WebGetArg("lh", tmp, sizeof(tmp));
+  WebGetArg(PSTR("lh"), tmp, sizeof(tmp));
   SettingsUpdateText(SET_SYSLOG_HOST, (!strlen(tmp)) ? SYS_LOG_HOST : tmp);
-  WebGetArg("lp", tmp, sizeof(tmp));
+  WebGetArg(PSTR("lp"), tmp, sizeof(tmp));
   Settings.syslog_port = (!strlen(tmp)) ? SYS_LOG_PORT : atoi(tmp);
-  WebGetArg("lt", tmp, sizeof(tmp));
+  WebGetArg(PSTR("lt"), tmp, sizeof(tmp));
   Settings.tele_period = (!strlen(tmp)) ? TELE_PERIOD : atoi(tmp);
   if ((Settings.tele_period > 0) && (Settings.tele_period < 10)) {
     Settings.tele_period = 10;   // Do not allow periods < 10 seconds
@@ -1868,7 +1869,7 @@ void HandleOtherConfiguration(void)
 
   AddLog_P(LOG_LEVEL_DEBUG, PSTR(D_LOG_HTTP D_CONFIGURE_OTHER));
 
-  if (Webserver->hasArg("save")) {
+  if (Webserver->hasArg(F("save"))) {
     OtherSaveSettings();
     WebRestart(1);
     return;
@@ -1932,15 +1933,15 @@ void OtherSaveSettings(void)
   char friendlyname[TOPSZ];
   char message[MAX_LOGSZ];
 
-  WebGetArg("dn", tmp, sizeof(tmp));
+  WebGetArg(PSTR("dn"), tmp, sizeof(tmp));
   SettingsUpdateText(SET_DEVICENAME, (!strlen(tmp)) ? "" : (!strcmp(tmp,"1")) ? SettingsText(SET_FRIENDLYNAME1) : tmp);
-  WebGetArg("wp", tmp, sizeof(tmp));
+  WebGetArg(PSTR("wp"), tmp, sizeof(tmp));
   SettingsUpdateText(SET_WEBPWD, (!strlen(tmp)) ? "" : (strchr(tmp,'*')) ? SettingsText(SET_WEBPWD) : tmp);
-  Settings.flag.mqtt_enabled = Webserver->hasArg("b1");  // SetOption3 - Enable MQTT
+  Settings.flag.mqtt_enabled = Webserver->hasArg(F("b1"));  // SetOption3 - Enable MQTT
 #ifdef USE_EMULATION
   UdpDisconnect();
 #if defined(USE_EMULATION_WEMO) || defined(USE_EMULATION_HUE)
-  WebGetArg("b2", tmp, sizeof(tmp));
+  WebGetArg(PSTR("b2"), tmp, sizeof(tmp));
   Settings.flag2.emulation = (!strlen(tmp)) ? 0 : atoi(tmp);
 #endif  // USE_EMULATION_WEMO || USE_EMULATION_HUE
 #endif  // USE_EMULATION
@@ -1951,14 +1952,14 @@ void OtherSaveSettings(void)
     snprintf_P(webindex, sizeof(webindex), PSTR("a%d"), i);
     WebGetArg(webindex, tmp, sizeof(tmp));
     snprintf_P(friendlyname, sizeof(friendlyname), PSTR(FRIENDLY_NAME"%d"), i +1);
-    SettingsUpdateText(SET_FRIENDLYNAME1 +i, (!strlen(tmp)) ? (i) ? friendlyname : FRIENDLY_NAME : tmp);
+    SettingsUpdateText(SET_FRIENDLYNAME1 +i, (!strlen(tmp)) ? (i) ? friendlyname : PSTR(FRIENDLY_NAME) : tmp);
     snprintf_P(message, sizeof(message), PSTR("%s%s %s"), message, (i) ? "," : "", SettingsText(SET_FRIENDLYNAME1 +i));
   }
   AddLogData(LOG_LEVEL_INFO, message);
 
-  WebGetArg("t1", tmp, sizeof(tmp));
+  WebGetArg(PSTR("t1"), tmp, sizeof(tmp));
   if (strlen(tmp)) {  // {"NAME":"12345678901234","GPIO":[255,255,255,255,255,255,255,255,255,255,255,255,255],"FLAG":255,"BASE":255}
-    snprintf_P(message, sizeof(message), PSTR(D_CMND_BACKLOG " " D_CMND_TEMPLATE " %s%s"), tmp, (Webserver->hasArg("t2")) ? "; " D_CMND_MODULE " 0" : "");
+    snprintf_P(message, sizeof(message), PSTR(D_CMND_BACKLOG " " D_CMND_TEMPLATE " %s%s"), tmp, (Webserver->hasArg(F("t2"))) ? PSTR("; " D_CMND_MODULE " 0") : "");
     ExecuteWebCommand(message, SRC_WEBGUI);
   }
 }
@@ -2034,7 +2035,7 @@ void HandleRestoreConfiguration(void)
   WSContentStart_P(PSTR(D_RESTORE_CONFIGURATION));
   WSContentSendStyle();
   WSContentSend_P(HTTP_FORM_RST);
-  WSContentSend_P(HTTP_FORM_RST_UPG, D_RESTORE);
+  WSContentSend_P(HTTP_FORM_RST_UPG, PSTR(D_RESTORE));
   if (WifiIsInManagerMode()) {
     WSContentSpaceButton(BUTTON_MAIN);
   } else {
@@ -2249,7 +2250,7 @@ void HandleUpgradeFirmware(void) {
   WSContentStart_P(PSTR(D_FIRMWARE_UPGRADE));
   WSContentSendStyle();
   WSContentSend_P(HTTP_FORM_UPG, SettingsText(SET_OTAURL));
-  WSContentSend_P(HTTP_FORM_RST_UPG, D_UPGRADE);
+  WSContentSend_P(HTTP_FORM_RST_UPG, PSTR(D_UPGRADE));
   WSContentSpaceButton(BUTTON_MAIN);
   WSContentStop();
 
@@ -2265,7 +2266,7 @@ void HandleUpgradeFirmwareStart(void) {
   WifiConfigCounter();
 
   char otaurl[TOPSZ];
-  WebGetArg("o", otaurl, sizeof(otaurl));
+  WebGetArg(PSTR("o"), otaurl, sizeof(otaurl));
   if (strlen(otaurl)) {
     snprintf_P(command, sizeof(command), PSTR(D_CMND_OTAURL " %s"), otaurl);
     ExecuteWebCommand(command, SRC_WEBGUI);
@@ -2668,9 +2669,9 @@ void HandleHttpCommand(void)
   if (!WebAuthenticate()) {
     // Prefer authorization via HTTP header (Basic auth), if it fails, use legacy method via GET parameters
     char tmp1[33];
-    WebGetArg("user", tmp1, sizeof(tmp1));
+    WebGetArg(PSTR("user"), tmp1, sizeof(tmp1));
     char tmp2[strlen(SettingsText(SET_WEBPWD)) + 1];
-    WebGetArg("password", tmp2, sizeof(tmp2));
+    WebGetArg(PSTR("password"), tmp2, sizeof(tmp2));
 
     if (!(!strcmp(tmp1, WEB_USERNAME) && !strcmp(tmp2, SettingsText(SET_WEBPWD)))) {
       WSContentBegin(401, CT_JSON);
@@ -2681,7 +2682,7 @@ void HandleHttpCommand(void)
   }
 
   WSContentBegin(200, CT_JSON);
-  String svalue = Webserver->arg("cmnd");
+  String svalue = Webserver->arg(F("cmnd"));
   if (svalue.length() && (svalue.length() < MQTT_MAX_PACKET_SIZE)) {
     uint32_t curridx = TasmotaGlobal.log_buffer_pointer;
     TasmotaGlobal.templog_level = LOG_LEVEL_INFO;
@@ -2717,7 +2718,7 @@ void HandleConsole(void)
 {
   if (!HttpCheckPriviledgedAccess()) { return; }
 
-  if (Webserver->hasArg("c2")) {      // Console refresh requested
+  if (Webserver->hasArg(F("c2"))) {      // Console refresh requested
     HandleConsoleRefresh();
     return;
   }
@@ -2734,14 +2735,14 @@ void HandleConsole(void)
 
 void HandleConsoleRefresh(void)
 {
-  String svalue = Webserver->arg("c1");
+  String svalue = Webserver->arg(F("c1"));
   if (svalue.length() && (svalue.length() < MQTT_MAX_PACKET_SIZE)) {
     AddLog_P(LOG_LEVEL_INFO, PSTR(D_LOG_COMMAND "%s"), svalue.c_str());
     ExecuteWebCommand((char*)svalue.c_str(), SRC_WEBCONSOLE);
   }
 
   char stmp[8];
-  WebGetArg("c2", stmp, sizeof(stmp));
+  WebGetArg(PSTR("c2"), stmp, sizeof(stmp));
   uint32_t index = 0;                // Initial start, dump all
   if (strlen(stmp)) { index = atoi(stmp); }
 
@@ -2758,7 +2759,7 @@ void HandleConsoleRefresh(void)
     if (len > sizeof(TasmotaGlobal.mqtt_data) -2) { len = sizeof(TasmotaGlobal.mqtt_data); }
     char stemp[len +1];
     strlcpy(stemp, line, len);
-    WSContentSend_P(PSTR("%s%s"), (cflg) ? "\n" : "", stemp);
+    WSContentSend_P(PSTR("%s%s"), (cflg) ? PSTR("\n") : "", stemp);
     cflg = true;
   }
   WSContentSend_P(PSTR("}1"));
@@ -2776,14 +2777,14 @@ void HandleNotFound(void)
 #ifdef USE_EMULATION
 #ifdef USE_EMULATION_HUE
   String path = Webserver->uri();
-  if ((EMUL_HUE == Settings.flag2.emulation) && (path.startsWith("/api"))) {
+  if ((EMUL_HUE == Settings.flag2.emulation) && (path.startsWith(F("/api")))) {
     HandleHueApi(&path);
   } else
 #endif  // USE_EMULATION_HUE
 #endif  // USE_EMULATION
   {
     WSContentBegin(404, CT_PLAIN);
-    WSContentSend_P(PSTR(D_FILE_NOT_FOUND "\n\nURI: %s\nMethod: %s\nArguments: %d\n"), Webserver->uri().c_str(), (Webserver->method() == HTTP_GET) ? "GET" : "POST", Webserver->args());
+    WSContentSend_P(PSTR(D_FILE_NOT_FOUND "\n\nURI: %s\nMethod: %s\nArguments: %d\n"), Webserver->uri().c_str(), (Webserver->method() == HTTP_GET) ? PSTR("GET") : PSTR("POST"), Webserver->args());
     for (uint32_t i = 0; i < Webserver->args(); i++) {
       WSContentSend_P(PSTR(" %s: %s\n"), Webserver->argName(i).c_str(), Webserver->arg(i).c_str());
     }
@@ -2978,7 +2979,7 @@ void CmndWebServer(void)
   }
   if (Settings.webserver) {
     Response_P(PSTR("{\"" D_CMND_WEBSERVER "\":\"" D_JSON_ACTIVE_FOR " %s " D_JSON_ON_DEVICE " %s " D_JSON_WITH_IP_ADDRESS " %s\"}"),
-      (2 == Settings.webserver) ? D_ADMIN : D_USER, NetworkHostname(), NetworkAddress().toString().c_str());
+      (2 == Settings.webserver) ? PSTR(D_ADMIN) : PSTR(D_USER), NetworkHostname(), NetworkAddress().toString().c_str());
   } else {
     ResponseCmndStateText(0);
   }
diff --git a/tasmota/xdrv_02_mqtt.ino b/tasmota/xdrv_02_mqtt.ino
index 6324a584b..bf4a9e6f9 100644
--- a/tasmota/xdrv_02_mqtt.ino
+++ b/tasmota/xdrv_02_mqtt.ino
@@ -156,7 +156,7 @@ void MqttInit(void) {
 
   // Detect AWS IoT and set default parameters
   String host = String(SettingsText(SET_MQTT_HOST));
-  if (host.indexOf(".iot.") && host.endsWith(".amazonaws.com")) {  // look for ".iot." and ".amazonaws.com" in the domain name
+  if (host.indexOf(F(".iot.")) && host.endsWith(F(".amazonaws.com"))) {  // look for ".iot." and ".amazonaws.com" in the domain name
     Settings.flag4.mqtt_no_retain = true;
   }
 
@@ -527,10 +527,10 @@ void MqttConnected(void) {
       if (Settings.webserver) {
 #if LWIP_IPV6
         Response_P(PSTR("{\"" D_JSON_WEBSERVER_MODE "\":\"%s\",\"" D_CMND_HOSTNAME "\":\"%s\",\"" D_CMND_IPADDRESS "\":\"%s\",\"IPv6Address\":\"%s\"}"),
-          (2 == Settings.webserver) ? D_ADMIN : D_USER, NetworkHostname(), NetworkAddress().toString().c_str(), WifiGetIPv6().c_str());
+          (2 == Settings.webserver) ? PSTR(D_ADMIN) : PSTR(D_USER), NetworkHostname(), NetworkAddress().toString().c_str(), WifiGetIPv6().c_str());
 #else
         Response_P(PSTR("{\"" D_JSON_WEBSERVER_MODE "\":\"%s\",\"" D_CMND_HOSTNAME "\":\"%s\",\"" D_CMND_IPADDRESS "\":\"%s\"}"),
-          (2 == Settings.webserver) ? D_ADMIN : D_USER, NetworkHostname(), NetworkAddress().toString().c_str());
+          (2 == Settings.webserver) ? PSTR(D_ADMIN) : PSTR(D_USER), NetworkHostname(), NetworkAddress().toString().c_str());
 #endif // LWIP_IPV6 = 1
         MqttPublishPrefixTopic_P(TELE, PSTR(D_RSLT_INFO "2"));
       }
@@ -787,7 +787,7 @@ void CmndMqttFingerprint(void) {
 
 void CmndMqttUser(void) {
   if (XdrvMailbox.data_len > 0) {
-    SettingsUpdateText(SET_MQTT_USER, (SC_CLEAR == Shortcut()) ? "" : (SC_DEFAULT == Shortcut()) ? MQTT_USER : XdrvMailbox.data);
+    SettingsUpdateText(SET_MQTT_USER, (SC_CLEAR == Shortcut()) ? "" : (SC_DEFAULT == Shortcut()) ? PSTR(MQTT_USER) : XdrvMailbox.data);
     TasmotaGlobal.restart_flag = 2;
   }
   ResponseCmndChar(SettingsText(SET_MQTT_USER));
@@ -795,7 +795,7 @@ void CmndMqttUser(void) {
 
 void CmndMqttPassword(void) {
   if (XdrvMailbox.data_len > 0) {
-    SettingsUpdateText(SET_MQTT_PWD, (SC_CLEAR == Shortcut()) ? "" : (SC_DEFAULT == Shortcut()) ? MQTT_PASS : XdrvMailbox.data);
+    SettingsUpdateText(SET_MQTT_PWD, (SC_CLEAR == Shortcut()) ? "" : (SC_DEFAULT == Shortcut()) ? PSTR(MQTT_PASS) : XdrvMailbox.data);
     ResponseCmndChar(SettingsText(SET_MQTT_PWD));
     TasmotaGlobal.restart_flag = 2;
   } else {
@@ -852,7 +852,7 @@ void CmndStateText(void) {
 
 void CmndMqttClient(void) {
   if (!XdrvMailbox.grpflg && (XdrvMailbox.data_len > 0)) {
-    SettingsUpdateText(SET_MQTT_CLIENT, (SC_DEFAULT == Shortcut()) ? MQTT_CLIENT_ID : XdrvMailbox.data);
+    SettingsUpdateText(SET_MQTT_CLIENT, (SC_DEFAULT == Shortcut()) ? PSTR(MQTT_CLIENT_ID) : XdrvMailbox.data);
     TasmotaGlobal.restart_flag = 2;
   }
   ResponseCmndChar(SettingsText(SET_MQTT_CLIENT));
@@ -882,7 +882,7 @@ void CmndPrefix(void) {
       if (XdrvMailbox.data_len > 0) {
         MakeValidMqtt(0, XdrvMailbox.data);
         SettingsUpdateText(SET_MQTTPREFIX1 + XdrvMailbox.index -1,
-          (SC_DEFAULT == Shortcut()) ? (1==XdrvMailbox.index) ? SUB_PREFIX : (2==XdrvMailbox.index) ? PUB_PREFIX : PUB_PREFIX2 : XdrvMailbox.data);
+          (SC_DEFAULT == Shortcut()) ? (1==XdrvMailbox.index) ? PSTR(SUB_PREFIX) : (2==XdrvMailbox.index) ? PSTR(PUB_PREFIX) : PSTR(PUB_PREFIX2) : XdrvMailbox.data);
         TasmotaGlobal.restart_flag = 2;
       }
       ResponseCmndIdxChar(SettingsText(SET_MQTTPREFIX1 + XdrvMailbox.index -1));
@@ -918,7 +918,7 @@ void CmndGroupTopic(void) {
       uint32_t settings_text_index = (1 == XdrvMailbox.index) ? SET_MQTT_GRP_TOPIC : SET_MQTT_GRP_TOPIC2 + XdrvMailbox.index - 2;
       MakeValidMqtt(0, XdrvMailbox.data);
       if (!strcmp(XdrvMailbox.data, TasmotaGlobal.mqtt_client)) { SetShortcutDefault(); }
-      SettingsUpdateText(settings_text_index, (SC_CLEAR == Shortcut()) ? "" : (SC_DEFAULT == Shortcut()) ? MQTT_GRPTOPIC : XdrvMailbox.data);
+      SettingsUpdateText(settings_text_index, (SC_CLEAR == Shortcut()) ? "" : (SC_DEFAULT == Shortcut()) ? PSTR(MQTT_GRPTOPIC) : XdrvMailbox.data);
 
       // Eliminate duplicates, have at least one and fill from index 1
       char stemp[MAX_GROUP_TOPICS][TOPSZ];
@@ -940,7 +940,7 @@ void CmndGroupTopic(void) {
         }
       }
       if (0 == read_index) {
-        SettingsUpdateText(SET_MQTT_GRP_TOPIC, MQTT_GRPTOPIC);
+        SettingsUpdateText(SET_MQTT_GRP_TOPIC, PSTR(MQTT_GRPTOPIC));
       } else {
         uint32_t write_index = 0;
         uint32_t real_index = SET_MQTT_GRP_TOPIC;
@@ -998,7 +998,7 @@ void CmndSwitchTopic(void) {
     switch (Shortcut()) {
       case SC_CLEAR: SettingsUpdateText(SET_MQTT_SWITCH_TOPIC, ""); break;
       case SC_DEFAULT: SettingsUpdateText(SET_MQTT_SWITCH_TOPIC, TasmotaGlobal.mqtt_topic); break;
-      case SC_USER: SettingsUpdateText(SET_MQTT_SWITCH_TOPIC, MQTT_SWITCH_TOPIC); break;
+      case SC_USER: SettingsUpdateText(SET_MQTT_SWITCH_TOPIC, PSTR(MQTT_SWITCH_TOPIC)); break;
       default: SettingsUpdateText(SET_MQTT_SWITCH_TOPIC, XdrvMailbox.data);
     }
   }
@@ -1266,7 +1266,7 @@ void HandleMqttConfiguration(void)
 
   AddLog_P(LOG_LEVEL_DEBUG, PSTR(D_LOG_HTTP D_CONFIGURE_MQTT));
 
-  if (Webserver->hasArg("save")) {
+  if (Webserver->hasArg(F("save"))) {
     MqttSaveSettings();
     WebRestart(1);
     return;
@@ -1282,11 +1282,11 @@ void HandleMqttConfiguration(void)
 #ifdef USE_MQTT_TLS
     Mqtt.mqtt_tls ? PSTR(" checked") : "",      // SetOption102 - Enable MQTT TLS
 #endif // USE_MQTT_TLS
-    Format(str, MQTT_CLIENT_ID, sizeof(str)), MQTT_CLIENT_ID, SettingsText(SET_MQTT_CLIENT));
+    Format(str, PSTR(MQTT_CLIENT_ID), sizeof(str)), PSTR(MQTT_CLIENT_ID), SettingsText(SET_MQTT_CLIENT));
   WSContentSend_P(HTTP_FORM_MQTT2,
     (!strlen(SettingsText(SET_MQTT_USER))) ? "0" : SettingsText(SET_MQTT_USER),
-    Format(str, MQTT_TOPIC, sizeof(str)), MQTT_TOPIC, SettingsText(SET_MQTT_TOPIC),
-    MQTT_FULLTOPIC, MQTT_FULLTOPIC, SettingsText(SET_MQTT_FULLTOPIC));
+    Format(str, PSTR(MQTT_TOPIC), sizeof(str)), PSTR(MQTT_TOPIC), SettingsText(SET_MQTT_TOPIC),
+    PSTR(MQTT_FULLTOPIC), PSTR(MQTT_FULLTOPIC), SettingsText(SET_MQTT_FULLTOPIC));
   WSContentSend_P(HTTP_FORM_END);
   WSContentSpaceButton(BUTTON_CONFIGURATION);
   WSContentStop();
@@ -1298,10 +1298,10 @@ void MqttSaveSettings(void)
   char stemp[TOPSZ];
   char stemp2[TOPSZ];
 
-  WebGetArg("mt", tmp, sizeof(tmp));
+  WebGetArg(PSTR("mt"), tmp, sizeof(tmp));
   strlcpy(stemp, (!strlen(tmp)) ? MQTT_TOPIC : tmp, sizeof(stemp));
   MakeValidMqtt(0, stemp);
-  WebGetArg("mf", tmp, sizeof(tmp));
+  WebGetArg(PSTR("mf"), tmp, sizeof(tmp));
   strlcpy(stemp2, (!strlen(tmp)) ? MQTT_FULLTOPIC : tmp, sizeof(stemp2));
   MakeValidMqtt(1, stemp2);
   if ((strcmp(stemp, SettingsText(SET_MQTT_TOPIC))) || (strcmp(stemp2, SettingsText(SET_MQTT_FULLTOPIC)))) {
@@ -1310,18 +1310,18 @@ void MqttSaveSettings(void)
   }
   SettingsUpdateText(SET_MQTT_TOPIC, stemp);
   SettingsUpdateText(SET_MQTT_FULLTOPIC, stemp2);
-  WebGetArg("mh", tmp, sizeof(tmp));
-  SettingsUpdateText(SET_MQTT_HOST, (!strlen(tmp)) ? MQTT_HOST : (!strcmp(tmp,"0")) ? "" : tmp);
-  WebGetArg("ml", tmp, sizeof(tmp));
+  WebGetArg(PSTR("mh"), tmp, sizeof(tmp));
+  SettingsUpdateText(SET_MQTT_HOST, (!strlen(tmp)) ? PSTR(MQTT_HOST) : (!strcmp(tmp,"0")) ? "" : tmp);
+  WebGetArg(PSTR("ml"), tmp, sizeof(tmp));
   Settings.mqtt_port = (!strlen(tmp)) ? MQTT_PORT : atoi(tmp);
 #ifdef USE_MQTT_TLS
-  Settings.flag4.mqtt_tls = Webserver->hasArg("b3");  // SetOption102 - Enable MQTT TLS
+  Settings.flag4.mqtt_tls = Webserver->hasArg(F("b3"));  // SetOption102 - Enable MQTT TLS
 #endif
-  WebGetArg("mc", tmp, sizeof(tmp));
-  SettingsUpdateText(SET_MQTT_CLIENT, (!strlen(tmp)) ? MQTT_CLIENT_ID : tmp);
-  WebGetArg("mu", tmp, sizeof(tmp));
-  SettingsUpdateText(SET_MQTT_USER, (!strlen(tmp)) ? MQTT_USER : (!strcmp(tmp,"0")) ? "" : tmp);
-  WebGetArg("mp", tmp, sizeof(tmp));
+  WebGetArg(PSTR("mc"), tmp, sizeof(tmp));
+  SettingsUpdateText(SET_MQTT_CLIENT, (!strlen(tmp)) ? PSTR(MQTT_CLIENT_ID) : tmp);
+  WebGetArg(PSTR("mu"), tmp, sizeof(tmp));
+  SettingsUpdateText(SET_MQTT_USER, (!strlen(tmp)) ? PSTR(MQTT_USER) : (!strcmp(tmp,"0")) ? "" : tmp);
+  WebGetArg(PSTR("mp"), tmp, sizeof(tmp));
   SettingsUpdateText(SET_MQTT_PWD, (!strlen(tmp)) ? "" : (!strcmp(tmp, D_ASTERISK_PWD)) ? SettingsText(SET_MQTT_PWD) : tmp);
   AddLog_P(LOG_LEVEL_INFO, PSTR(D_LOG_MQTT D_CMND_MQTTHOST " %s, " D_CMND_MQTTPORT " %d, " D_CMND_MQTTCLIENT " %s, " D_CMND_MQTTUSER " %s, " D_CMND_TOPIC " %s, " D_CMND_FULLTOPIC " %s"),
     SettingsText(SET_MQTT_HOST), Settings.mqtt_port, SettingsText(SET_MQTT_CLIENT), SettingsText(SET_MQTT_USER), SettingsText(SET_MQTT_TOPIC), SettingsText(SET_MQTT_FULLTOPIC));
diff --git a/tasmota/xdrv_04_light.ino b/tasmota/xdrv_04_light.ino
index 90d94ffb7..7e0907dd1 100644
--- a/tasmota/xdrv_04_light.ino
+++ b/tasmota/xdrv_04_light.ino
@@ -2625,7 +2625,7 @@ void CmndWakeup(void)
   Light.wakeup_active = 3;
   Settings.light_scheme = LS_WAKEUP;
   LightPowerOn();
-  ResponseCmndChar(D_JSON_STARTED);
+  ResponseCmndChar(PSTR(D_JSON_STARTED));
 }
 
 void CmndColorTemperature(void)
diff --git a/tasmota/xdrv_07_domoticz.ino b/tasmota/xdrv_07_domoticz.ino
index 82b769963..b982a58b1 100644
--- a/tasmota/xdrv_07_domoticz.ino
+++ b/tasmota/xdrv_07_domoticz.ino
@@ -546,7 +546,7 @@ void HandleDomoticzConfiguration(void) {
 
   AddLog_P(LOG_LEVEL_DEBUG, PSTR(D_LOG_HTTP D_CONFIGURE_DOMOTICZ));
 
-  if (Webserver->hasArg("save")) {
+  if (Webserver->hasArg(F("save"))) {
     DomoticzSaveSettings();
     WebRestart(1);
     return;
@@ -605,7 +605,7 @@ void DomoticzSaveSettings(void) {
     Settings.domoticz_sensor_idx[i] = (!strlen(tmp)) ? 0 : atoi(tmp);
     snprintf_P(ssensor_indices, sizeof(ssensor_indices), PSTR("%s%s%d"), ssensor_indices, (strlen(ssensor_indices)) ? "," : "",  Settings.domoticz_sensor_idx[i]);
   }
-  WebGetArg("ut", tmp, sizeof(tmp));
+  WebGetArg(PSTR("ut"), tmp, sizeof(tmp));
   Settings.domoticz_update_timer = (!strlen(tmp)) ? DOMOTICZ_UPDATE_TIMER : atoi(tmp);
 
   AddLog_P(LOG_LEVEL_INFO, PSTR(D_LOG_DOMOTICZ D_CMND_IDX " %d,%d,%d,%d, " D_CMND_KEYIDX " %d,%d,%d,%d, " D_CMND_SWITCHIDX " %d,%d,%d,%d, " D_CMND_SENSORIDX " %s, " D_CMND_UPDATETIMER " %d"),
diff --git a/tasmota/xdrv_09_timers.ino b/tasmota/xdrv_09_timers.ino
index 0f6292e13..a33204906 100644
--- a/tasmota/xdrv_09_timers.ino
+++ b/tasmota/xdrv_09_timers.ino
@@ -841,7 +841,7 @@ void HandleTimerConfiguration(void)
 
   AddLog_P(LOG_LEVEL_DEBUG, PSTR(D_LOG_HTTP D_CONFIGURE_TIMER));
 
-  if (Webserver->hasArg("save")) {
+  if (Webserver->hasArg(F("save"))) {
     TimerSaveSettings();
     HandleConfiguration();
     return;
@@ -883,8 +883,8 @@ void TimerSaveSettings(void)
   char message[32 + (MAX_TIMERS *11)];  // MQT: Timers 0,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000
   Timer timer;
 
-  Settings.flag3.timers_enable = Webserver->hasArg("e0");  // CMND_TIMERS
-  WebGetArg("t0", tmp, sizeof(tmp));
+  Settings.flag3.timers_enable = Webserver->hasArg(F("e0"));  // CMND_TIMERS
+  WebGetArg(PSTR("t0"), tmp, sizeof(tmp));
   char *p = tmp;
   snprintf_P(message, sizeof(message), PSTR(D_LOG_MQTT D_CMND_TIMERS " %d"), Settings.flag3.timers_enable);  // CMND_TIMERS
   for (uint32_t i = 0; i < MAX_TIMERS; i++) {
diff --git a/tasmota/xdrv_10_rules.ino b/tasmota/xdrv_10_rules.ino
index 637a3b963..4a6d3c9c1 100644
--- a/tasmota/xdrv_10_rules.ino
+++ b/tasmota/xdrv_10_rules.ino
@@ -416,7 +416,7 @@ bool RulesRuleMatch(uint8_t rule_set, String &event, String &rule, bool stop_all
   // Step1: Analyse rule
   String rule_expr = rule;                             // "TELE-INA219#CURRENT>0.100"
   if (Rules.teleperiod) {
-    int ppos = rule_expr.indexOf("TELE-");             // "TELE-INA219#CURRENT>0.100" or "INA219#CURRENT>0.100"
+    int ppos = rule_expr.indexOf(F("TELE-"));             // "TELE-INA219#CURRENT>0.100" or "INA219#CURRENT>0.100"
     if (ppos == -1) { return false; }                  // No pre-amble in rule
     rule_expr = rule.substring(5);                     // "INA219#CURRENT>0.100" or "SYSTEM#BOOT"
   }
@@ -494,7 +494,7 @@ bool RulesRuleMatch(uint8_t rule_set, String &event, String &rule, bool stop_all
   // Step2: Search rule_name
   int pos;
   int rule_name_idx = 0;
-  if ((pos = rule_name.indexOf("[")) > 0) {            // "SUBTYPE1#CURRENT[1]"
+  if ((pos = rule_name.indexOf(F("["))) > 0) {            // "SUBTYPE1#CURRENT[1]"
     rule_name_idx = rule_name.substring(pos +1).toInt();
     if ((rule_name_idx < 1) || (rule_name_idx > 6)) {  // Allow indexes 1 to 6
       rule_name_idx = 1;
@@ -515,7 +515,7 @@ bool RulesRuleMatch(uint8_t rule_set, String &event, String &rule, bool stop_all
   }
   String subtype;
   uint32_t i = 0;
-  while ((pos = rule_name.indexOf("#")) > 0) {         // "SUBTYPE1#SUBTYPE2#CURRENT"
+  while ((pos = rule_name.indexOf(F("#"))) > 0) {         // "SUBTYPE1#SUBTYPE2#CURRENT"
     subtype = rule_name.substring(0, pos);
     obj = obj[subtype.c_str()].getObject();
     if (!obj) { return false; }                        // not found
@@ -686,14 +686,14 @@ bool RuleSetProcess(uint8_t rule_set, String &event_saved)
 
     String rule = rules;
     rule.toUpperCase();                                   // "ON INA219#CURRENT>0.100 DO BACKLOG DIMMER 10;COLOR 100000 ENDON"
-    if (!rule.startsWith("ON ")) { return serviced; }     // Bad syntax - Nothing to start on
+    if (!rule.startsWith(F("ON "))) { return serviced; }     // Bad syntax - Nothing to start on
 
-    int pevt = rule.indexOf(" DO ");
+    int pevt = rule.indexOf(F(" DO "));
     if (pevt == -1) { return serviced; }                  // Bad syntax - Nothing to do
     String event_trigger = rule.substring(3, pevt);       // "INA219#CURRENT>0.100"
 
-    plen = rule.indexOf(" ENDON");
-    plen2 = rule.indexOf(" BREAK");
+    plen = rule.indexOf(F(" ENDON"));
+    plen2 = rule.indexOf(F(" BREAK"));
     if ((plen == -1) && (plen2 == -1)) { return serviced; } // Bad syntax - No ENDON neither BREAK
 
     if (plen == -1) { plen = 9999; }
@@ -717,10 +717,10 @@ bool RuleSetProcess(uint8_t rule_set, String &event_saved)
 
 //      if (!ucommand.startsWith("BACKLOG")) { commands = "backlog " + commands; }  // Always use Backlog to prevent power race exception
       // Use Backlog with event to prevent rule event loop exception unless IF is used which uses an implicit backlog
-      if ((ucommand.indexOf("IF ") == -1) &&
-          (ucommand.indexOf("EVENT ") != -1) &&
-          (ucommand.indexOf("BACKLOG ") == -1)) {
-        commands = "backlog " + commands;
+      if ((ucommand.indexOf(F("IF ")) == -1) &&
+          (ucommand.indexOf(F("EVENT ")) != -1) &&
+          (ucommand.indexOf(F("BACKLOG ")) == -1)) {
+        commands = String(F("backlog ")) + commands;
       }
 
       RulesVarReplace(commands, F("%VALUE%"), Rules.event_value);
diff --git a/tasmota/xdrv_12_home_assistant.ino b/tasmota/xdrv_12_home_assistant.ino
index bf4664886..0120615e0 100644
--- a/tasmota/xdrv_12_home_assistant.ino
+++ b/tasmota/xdrv_12_home_assistant.ino
@@ -294,7 +294,7 @@ void NewHAssDiscovery(void)
   for (uint32_t i = 0; i < MAX_FRIENDLYNAMES; i++) {
     char fname[TOPSZ];
     snprintf_P(fname, sizeof(fname), PSTR("\"%s\""), EscapeJSONString(SettingsText(SET_FRIENDLYNAME1 +i)).c_str());
-    snprintf_P(stemp2, sizeof(stemp2), PSTR("%s%s%s"), stemp2, (i > 0 ? "," : ""), (i < maxfn) ? fname : "null");
+    snprintf_P(stemp2, sizeof(stemp2), PSTR("%s%s%s"), stemp2, (i > 0 ? "," : ""), (i < maxfn) ? fname : PSTR("null"));
   }
 
   stemp3[0] = '\0';
@@ -304,7 +304,7 @@ void NewHAssDiscovery(void)
     char sname[TOPSZ];
     snprintf_P(sname, sizeof(sname), PSTR("\"%s\""), GetSwitchText(i).c_str());
     snprintf_P(stemp3, sizeof(stemp3), PSTR("%s%s%d"), stemp3, (i > 0 ? "," : ""), (PinUsed(GPIO_SWT1, i) & Settings.flag5.mqtt_switches) ? Settings.switchmode[i] : -1);
-    snprintf_P(stemp4, sizeof(stemp4), PSTR("%s%s%s"), stemp4, (i > 0 ? "," : ""), (PinUsed(GPIO_SWT1, i) & Settings.flag5.mqtt_switches) ? sname : "null");
+    snprintf_P(stemp4, sizeof(stemp4), PSTR("%s%s%s"), stemp4, (i > 0 ? "," : ""), (PinUsed(GPIO_SWT1, i) & Settings.flag5.mqtt_switches) ? sname : PSTR("null"));
   }
 
   stemp5[0] = '\0';
@@ -338,7 +338,7 @@ void NewHAssDiscovery(void)
   if (!Settings.flag.hass_discovery) { // HassDiscoveryRelays(relays)
     Response_P(HASS_DISCOVER_DEVICE, WiFi.localIP().toString().c_str(), SettingsText(SET_DEVICENAME),
               stemp2, TasmotaGlobal.hostname, unique_id, ModuleName().c_str(), TuyaMod, iFanMod, GetStateText(0), GetStateText(1), GetStateText(2), GetStateText(3),
-              TasmotaGlobal.version, TasmotaGlobal.mqtt_topic, SettingsText(SET_MQTT_FULLTOPIC), SUB_PREFIX, PUB_PREFIX, PUB_PREFIX2, Hass.RelLst, stemp3, stemp4,
+              TasmotaGlobal.version, TasmotaGlobal.mqtt_topic, SettingsText(SET_MQTT_FULLTOPIC), PSTR(SUB_PREFIX), PSTR(PUB_PREFIX), PSTR(PUB_PREFIX2), Hass.RelLst, stemp3, stemp4,
               stemp5, Settings.flag.mqtt_response, Settings.flag.button_swap, Settings.flag.button_single, Settings.flag.decimal_text, Settings.flag.not_power_linked,
               Settings.flag.hass_light, Settings.flag3.pwm_multi_channels, Settings.flag3.mqtt_buttons, Settings.flag4.alexa_ct_range, Settings.flag5.mqtt_switches,
               Settings.flag5.fade_fixed_duration, light_controller.isCTRGBLinked(), Light.subtype, stemp6);
diff --git a/tasmota/xdrv_16_tuyamcu.ino b/tasmota/xdrv_16_tuyamcu.ino
index a291d2e11..7535d29c5 100644
--- a/tasmota/xdrv_16_tuyamcu.ino
+++ b/tasmota/xdrv_16_tuyamcu.ino
@@ -1295,7 +1295,7 @@ void TuyaSensorsShow(bool json)
 
         GetTextIndexed(sname, sizeof(sname), (sensor-71), kTuyaSensors);
         ResponseAppend_P(PSTR("\"%s\":%s"), sname,
-                        (Tuya.SensorsValid[sensor-71] ? dtostrfd(Tuya.Sensors[sensor-71], res, tempval) : "null"));
+                        (Tuya.SensorsValid[sensor-71] ? dtostrfd(Tuya.Sensors[sensor-71], res, tempval) : PSTR("null")));
         added = true;
       }
   #ifdef USE_WEBSERVER
diff --git a/tasmota/xdrv_20_hue.ino b/tasmota/xdrv_20_hue.ino
index 4da625847..013e22a98 100644
--- a/tasmota/xdrv_20_hue.ino
+++ b/tasmota/xdrv_20_hue.ino
@@ -429,9 +429,9 @@ void HandleUpnpSetupHue(void)
 {
   AddLog_P(LOG_LEVEL_DEBUG, PSTR(D_LOG_HTTP D_HUE_BRIDGE_SETUP));
   String description_xml = Decompress(HUE_DESCRIPTION_XML_COMPRESSED,HUE_DESCRIPTION_XML_SIZE);
-  description_xml.replace("{x1", WiFi.localIP().toString());
-  description_xml.replace("{x2", HueUuid());
-  description_xml.replace("{x3", HueSerialnumber());
+  description_xml.replace(F("{x1"), WiFi.localIP().toString());
+  description_xml.replace(F("{x2"), HueUuid());
+  description_xml.replace(F("{x3"), HueSerialnumber());
   WSSend(200, CT_XML, description_xml);
 }
 
@@ -439,19 +439,19 @@ void HueNotImplemented(String *path)
 {
   AddLog_P(LOG_LEVEL_DEBUG_MORE, PSTR(D_LOG_HTTP D_HUE_API_NOT_IMPLEMENTED " (%s)"), path->c_str());
 
-  WSSend(200, CT_JSON, "{}");
+  WSSend(200, CT_JSON, PSTR("{}"));
 }
 
 void HueConfigResponse(String *response)
 {
   *response += Decompress(HueConfigResponse_JSON, HueConfigResponse_JSON_SIZE);
-  response->replace("{ma", WiFi.macAddress());
-  response->replace("{ip", WiFi.localIP().toString());
-  response->replace("{ms", WiFi.subnetMask().toString());
-  response->replace("{gw", WiFi.gatewayIP().toString());
-  response->replace("{br", HueBridgeId());
-  response->replace("{dt", GetDateAndTime(DT_UTC));
-  response->replace("{id", GetHueUserId());
+  response->replace(F("{ma"), WiFi.macAddress());
+  response->replace(F("{ip"), WiFi.localIP().toString());
+  response->replace(F("{ms"), WiFi.subnetMask().toString());
+  response->replace(F("{gw"), WiFi.gatewayIP().toString());
+  response->replace(F("{br"), HueBridgeId());
+  response->replace(F("{dt"), GetDateAndTime(DT_UTC));
+  response->replace(F("{id"), GetHueUserId());
 }
 
 void HueConfig(String *path)
@@ -534,13 +534,13 @@ void HueLightStatus1(uint8_t device, String *response)
   char * buf = (char*) malloc(buf_size);     // temp buffer for strings, avoid stack
   UnishoxStrings msg(HUE_LIGHTS);
 
-  snprintf_P(buf, buf_size, PSTR("{\"on\":%s,"), (TasmotaGlobal.power & (1 << (device-1))) ? "true" : "false");
+  snprintf_P(buf, buf_size, PSTR("{\"on\":%s,"), (TasmotaGlobal.power & (1 << (device-1))) ? PSTR("true") : PSTR("false"));
   // Brightness for all devices with PWM
   if ((1 == echo_gen) || (LST_SINGLE <= local_light_subtype)) { // force dimmer for 1st gen Echo
     snprintf_P(buf, buf_size, PSTR("%s\"bri\":%d,"), buf, bri);
   }
   if (LST_COLDWARM <= local_light_subtype) {
-    snprintf_P(buf, buf_size, PSTR("%s\"colormode\":\"%s\","), buf, g_gotct ? "ct" : "hs");
+    snprintf_P(buf, buf_size, PSTR("%s\"colormode\":\"%s\","), buf, g_gotct ? PSTR("ct") : PSTR("hs"));
   }
   if (LST_RGB <= local_light_subtype) {  // colors
     if (prev_x_str[0] && prev_y_str[0]) {
@@ -680,7 +680,7 @@ void HueGlobalConfig(String *path) {
 #endif // USE_ZIGBEE
   response += F("},\"groups\":{},\"schedules\":{},\"config\":");
   HueConfigResponse(&response);
-  response += "}";
+  response += F("}");
   WSSend(200, CT_JSON, response);
 }
 
@@ -700,7 +700,7 @@ void CheckHue(String * response, bool &appending) {
   for (uint32_t i = 1; i <= maxhue; i++) {
     if (HueActive(i)) {
       if (appending) { *response += ","; }
-      *response += "\"";
+      *response += F("\"");
       *response += EncodeLightId(i);
       *response += F("\":{\"state\":");
       HueLightStatus1(i, response);
@@ -735,7 +735,7 @@ void HueLightsCommand(uint8_t device, uint32_t device_id, String &response) {
       on = hue_on.getBool();
       snprintf_P(buf, buf_size,
                  msg[HUE_RESP_ON],
-                 device_id, on ? "true" : "false");
+                 device_id, on ? PSTR("true") : PSTR("false"));
 
 #ifdef USE_SHUTTER
       if (ShutterState(device)) {
@@ -778,7 +778,7 @@ void HueLightsCommand(uint8_t device, uint32_t device_id, String &response) {
       if (resp) { response += ","; }
       snprintf_P(buf, buf_size,
                  msg[HUE_RESP_NUM],
-                 device_id, "bri", bri);
+                 device_id, PSTR("bri"), bri);
       response += buf;
       if (LST_SINGLE <= Light.subtype) {
         // extend bri value if set to max
@@ -824,7 +824,7 @@ void HueLightsCommand(uint8_t device, uint32_t device_id, String &response) {
       if (resp) { response += ","; }
       snprintf_P(buf, buf_size,
                  msg[HUE_RESP_NUM],
-                 device_id, "hue", hue);
+                 device_id, PSTR("hue"), hue);
       response += buf;
       if (LST_RGB <= Light.subtype) {
         // change range from 0..65535 to 0..360
@@ -843,7 +843,7 @@ void HueLightsCommand(uint8_t device, uint32_t device_id, String &response) {
       if (resp) { response += ","; }
       snprintf_P(buf, buf_size,
                  msg[HUE_RESP_NUM],
-                 device_id, "sat", sat);
+                 device_id, PSTR("sat"), sat);
       response += buf;
       if (LST_RGB <= Light.subtype) {
         // extend sat value if set to max
@@ -862,7 +862,7 @@ void HueLightsCommand(uint8_t device, uint32_t device_id, String &response) {
       if (resp) { response += ","; }
       snprintf_P(buf, buf_size,
                  msg[HUE_RESP_NUM],
-                 device_id, "ct", ct);
+                 device_id, PSTR("ct"), ct);
       response += buf;
       if ((LST_COLDWARM == Light.subtype) || (LST_RGBW <= Light.subtype)) {
         g_gotct = true;
@@ -923,7 +923,7 @@ void HueLights(String *path)
 
   path->remove(0,path->indexOf(F("/lights")));          // Remove until /lights
   if (path->endsWith(F("/lights"))) {                   // Got /lights
-    response = "{";
+    response = F("{");
     bool appending = false;
 #ifdef USE_LIGHT
     CheckHue(&response, appending);
@@ -934,7 +934,7 @@ void HueLights(String *path)
 #ifdef USE_SCRIPT_HUE
     Script_Check_Hue(&response);
 #endif
-    response += "}";
+    response += F("}");
   }
   else if (path->endsWith(F("/state"))) {               // Got ID/state
     path->remove(0,8);                               // Remove /lights/
@@ -992,7 +992,7 @@ void HueLights(String *path)
 #endif // USE_LIGHT
   }
   else {
-    response = "{}";
+    response = F("{}");
     code = 406;
   }
   exit:
@@ -1005,24 +1005,24 @@ void HueGroups(String *path)
 /*
  * http://tasmota/api/username/groups?1={"name":"Woonkamer","lights":[],"type":"Room","class":"Living room"})
  */
-  String response = "{}";
+  String response(F("{}"));
   uint8_t maxhue = (TasmotaGlobal.devices_present > MAX_HUE_DEVICES) ? MAX_HUE_DEVICES : TasmotaGlobal.devices_present;
   //AddLog_P(LOG_LEVEL_DEBUG_MORE, PSTR(D_LOG_HTTP D_HUE " HueGroups (%s)"), path->c_str());
 
-  if (path->endsWith("/0")) {
+  if (path->endsWith(F("/0"))) {
     UnishoxStrings msg(HUE_LIGHTS);
     response = msg[HUE_GROUP0_STATUS_JSON];
     String lights = F("\"1\"");
     for (uint32_t i = 2; i <= maxhue; i++) {
-      lights += ",\"";
+      lights += F(",\"");
       lights += EncodeLightId(i);
-      lights += "\"";
+      lights += F("\"");
     }
 
 #ifdef USE_ZIGBEE
     ZigbeeHueGroups(&response);
 #endif // USE_ZIGBEE
-    response.replace("{l1", lights);
+    response.replace(F("{l1"), lights);
 #ifdef USE_LIGHT
     HueLightStatus1(1, &response);
 #endif // USE_LIGHT
diff --git a/tasmota/xdrv_23_zigbee_1z_libs.ino b/tasmota/xdrv_23_zigbee_1z_libs.ino
index 4e018a21e..a228798e2 100644
--- a/tasmota/xdrv_23_zigbee_1z_libs.ino
+++ b/tasmota/xdrv_23_zigbee_1z_libs.ino
@@ -579,7 +579,7 @@ String Z_attribute::toString(bool prefix_comma) const {
   // value part
   switch (type) {
   case Za_type::Za_none:
-    res += "null";
+    res += F("null");
     break;
   case Za_type::Za_bool:
     res += val.uval32 ? F("true") : F("false");
@@ -638,7 +638,9 @@ String Z_attribute::toString(bool prefix_comma) const {
     if (val.arrval) {
       res += val.arrval->toString();
     } else {
-      res += "[]";
+      // res += '[';
+      // res += ']';
+      res += F("[]");
     }
     break;
   }
diff --git a/tasmota/xdrv_23_zigbee_2a_devices_impl.ino b/tasmota/xdrv_23_zigbee_2a_devices_impl.ino
index 7d850ef5a..55a98a748 100644
--- a/tasmota/xdrv_23_zigbee_2a_devices_impl.ino
+++ b/tasmota/xdrv_23_zigbee_2a_devices_impl.ino
@@ -556,7 +556,7 @@ void Z_Device::jsonPublishAttrList(const char * json_prefix, const Z_attribute_l
     if (Settings.flag5.zb_received_as_subtopic)
       GetTopic_P(stopic, TELE, subtopic, json_prefix);
     else
-      GetTopic_P(stopic, TELE, subtopic, D_RSLT_SENSOR);
+      GetTopic_P(stopic, TELE, subtopic, PSTR(D_RSLT_SENSOR));
     MqttPublish(stopic, Settings.flag.mqtt_sensor_retain);
   } else {
     MqttPublishPrefixTopic_P(TELE, PSTR(D_RSLT_SENSOR), Settings.flag.mqtt_sensor_retain);
diff --git a/tasmota/xdrv_23_zigbee_3_hue.ino b/tasmota/xdrv_23_zigbee_3_hue.ino
index a77c8b67f..d71a8c3a9 100644
--- a/tasmota/xdrv_23_zigbee_3_hue.ino
+++ b/tasmota/xdrv_23_zigbee_3_hue.ino
@@ -62,13 +62,13 @@ void HueLightStatus1Zigbee(uint16_t shortaddr, uint8_t local_light_subtype, Stri
   const size_t buf_size = 256;
   char * buf = (char*) malloc(buf_size);     // temp buffer for strings, avoid stack
 
-  snprintf_P(buf, buf_size, PSTR("{\"on\":%s,"), power ? "true" : "false");
+  snprintf_P(buf, buf_size, PSTR("{\"on\":%s,"), power ? PSTR("true") : PSTR("false"));
   // Brightness for all devices with PWM
   if ((1 == echo_gen) || (LST_SINGLE <= local_light_subtype)) { // force dimmer for 1st gen Echo
     snprintf_P(buf, buf_size, PSTR("%s\"bri\":%d,"), buf, bri);
   }
   if (LST_COLDWARM <= local_light_subtype) {
-    snprintf_P(buf, buf_size, PSTR("%s\"colormode\":\"%s\","), buf, (0 == colormode) ? "hs" : (1 == colormode) ? "xy" : "ct");
+    snprintf_P(buf, buf_size, PSTR("%s\"colormode\":\"%s\","), buf, (0 == colormode) ? PSTR("hs") : (1 == colormode) ? PSTR("xy") : PSTR("ct"));
   }
   if (LST_RGB <= local_light_subtype) {  // colors
     if (prev_x_str[0] && prev_y_str[0]) {
@@ -83,7 +83,7 @@ void HueLightStatus1Zigbee(uint16_t shortaddr, uint8_t local_light_subtype, Stri
   if (LST_COLDWARM == local_light_subtype || LST_RGBW <= local_light_subtype) {  // white temp
     snprintf_P(buf, buf_size, PSTR("%s\"ct\":%d,"), buf, ct > 0 ? ct : 284);
   }
-  snprintf_P(buf, buf_size, HUE_LIGHTS_STATUS_JSON1_SUFFIX_ZIGBEE, buf, reachable ? "true" : "false");
+  snprintf_P(buf, buf_size, HUE_LIGHTS_STATUS_JSON1_SUFFIX_ZIGBEE, buf, reachable ? PSTR("true") : PSTR("false"));
 
   *response += buf;
   free(buf);
@@ -233,7 +233,7 @@ void ZigbeeHandleHue(uint16_t shortaddr, uint32_t device_id, String &response) {
       on = hue_on.getBool();
       snprintf_P(buf, buf_size,
                  msg[HUE_RESP_ON],
-                 device_id, on ? "true" : "false");
+                 device_id, on ? PSTR("true") : PSTR("false"));
 
       if (on) {
         ZigbeeHuePower(shortaddr, 0x01);
@@ -252,7 +252,7 @@ void ZigbeeHandleHue(uint16_t shortaddr, uint32_t device_id, String &response) {
       if (resp) { response += ","; }
       snprintf_P(buf, buf_size,
                  msg[HUE_RESP_NUM],
-                 device_id, "bri", bri);
+                 device_id, PSTR("bri"), bri);
       response += buf;
       if (LST_SINGLE <= bulbtype) {
         // extend bri value if set to max
@@ -293,7 +293,7 @@ void ZigbeeHandleHue(uint16_t shortaddr, uint32_t device_id, String &response) {
       if (resp) { response += ","; }
       snprintf_P(buf, buf_size,
                  msg[HUE_RESP_NUM],
-                 device_id, "hue", hue);
+                 device_id, PSTR("hue"), hue);
       response += buf;
       if (LST_RGB <= bulbtype) {
         // change range from 0..65535 to 0..360
@@ -311,7 +311,7 @@ void ZigbeeHandleHue(uint16_t shortaddr, uint32_t device_id, String &response) {
       if (resp) { response += ","; }
       snprintf_P(buf, buf_size,
                  msg[HUE_RESP_NUM],
-                 device_id, "sat", sat);
+                 device_id, PSTR("sat"), sat);
       response += buf;
       if (LST_RGB <= bulbtype) {
         // extend sat value if set to max
@@ -332,7 +332,7 @@ void ZigbeeHandleHue(uint16_t shortaddr, uint32_t device_id, String &response) {
       if (resp) { response += ","; }
       snprintf_P(buf, buf_size,
                  msg[HUE_RESP_NUM],
-                 device_id, "ct", ct);
+                 device_id, PSTR("ct"), ct);
       response += buf;
       if ((LST_COLDWARM == bulbtype) || (LST_RGBW <= bulbtype)) {
         ZigbeeHueCT(shortaddr, ct);
diff --git a/tasmota/xdrv_23_zigbee_A_impl.ino b/tasmota/xdrv_23_zigbee_A_impl.ino
index ec9a454ac..673f1ff8d 100644
--- a/tasmota/xdrv_23_zigbee_A_impl.ino
+++ b/tasmota/xdrv_23_zigbee_A_impl.ino
@@ -2092,7 +2092,7 @@ void ZigbeeMapRefresh(void) {
   if ((!zigbee.init_phase) && (!zigbee.mapping_in_progress)) {
     ZigbeeMapAllDevices();
   }
-  Webserver->sendHeader("Location","/zbm");        // Add a header to respond with a new location for the browser to go to the home page again
+  Webserver->sendHeader(F("Location"),F("/zbm"));        // Add a header to respond with a new location for the browser to go to the home page again
   Webserver->send(302);
 }
 
diff --git a/tasmota/xdrv_38_ping.ino b/tasmota/xdrv_38_ping.ino
index 3f87a54bb..0974697fe 100644
--- a/tasmota/xdrv_38_ping.ino
+++ b/tasmota/xdrv_38_ping.ino
@@ -303,7 +303,7 @@ void PingResponsePoll(void) {
                       ",\"AvgTime\":%d"
                       "}}}"),
                       ping->hostname.c_str(),
-                      success ? "true" : "false",
+                      success ? PSTR("true") : PSTR("false"),
                       ip & 0xFF, (ip >> 8) & 0xFF, (ip >> 16) & 0xFF, ip >> 24,
                       success,
                       ping->timeout_count,
diff --git a/tasmota/xdrv_40_telegram.ino b/tasmota/xdrv_40_telegram.ino
index ec230e792..0ceefa3a7 100644
--- a/tasmota/xdrv_40_telegram.ino
+++ b/tasmota/xdrv_40_telegram.ino
@@ -434,14 +434,14 @@ void CmndTmChatId(void) {
 
 void CmndTmSend(void) {
   if (!Telegram.send_enable || !strlen(SettingsText(SET_TELEGRAM_CHATID))) {
-    ResponseCmndChar(D_JSON_FAILED);
+    ResponseCmndChar(PSTR(D_JSON_FAILED));
     return;
   }
   if (XdrvMailbox.data_len > 0) {
     String message = XdrvMailbox.data;
     String chat_id = SettingsText(SET_TELEGRAM_CHATID);
     if (!TelegramSendMessage(chat_id.toInt(), message)) {
-      ResponseCmndChar(D_JSON_FAILED);
+      ResponseCmndChar(PSTR(D_JSON_FAILED));
       return;
     }
   }
diff --git a/tasmota/xdrv_50_filesystem.ino b/tasmota/xdrv_50_filesystem.ino
index fb12e3b9d..dfca83cef 100644
--- a/tasmota/xdrv_50_filesystem.ino
+++ b/tasmota/xdrv_50_filesystem.ino
@@ -391,7 +391,7 @@ void UFSDelete(void) {
       result = (ufs_type && ufsp->remove(XdrvMailbox.data));
     }
     if (!result) {
-      ResponseCmndChar(D_JSON_FAILED);
+      ResponseCmndChar(PSTR(D_JSON_FAILED));
     } else {
       ResponseCmndDone();
     }
@@ -454,8 +454,8 @@ void UfsDirectory(void) {
 
   strcpy(ufs_path, "/");
 
-  if (Webserver->hasArg("download")) {
-    String stmp = Webserver->arg("download");
+  if (Webserver->hasArg(F("download"))) {
+    String stmp = Webserver->arg(F("download"));
     char *cp = (char*)stmp.c_str();
     if (UfsDownloadFile(cp)) {
       // is directory
@@ -465,8 +465,8 @@ void UfsDirectory(void) {
     }
   }
 
-  if (Webserver->hasArg("dir")) {
-    String stmp = Webserver->arg("dir");
+  if (Webserver->hasArg(F("dir"))) {
+    String stmp = Webserver->arg(F("dir"));
     ufs_dir = atoi(stmp.c_str());
     if (ufs_dir == 1) {
       dfsp = ufsp;
@@ -477,8 +477,8 @@ void UfsDirectory(void) {
     }
   }
 
-  if (Webserver->hasArg("delete")) {
-    String stmp = Webserver->arg("delete");
+  if (Webserver->hasArg(F("delete"))) {
+    String stmp = Webserver->arg(F("delete"));
     char *cp = (char*)stmp.c_str();
     dfsp->remove(cp);
   }
@@ -498,7 +498,7 @@ void UfsDirectory(void) {
   }
   WSContentSend_P(UFS_FORM_FILE_UPGc2);
 
-  WSContentSend_P(UFS_FORM_FILE_UPG, D_SCRIPT_UPLOAD);
+  WSContentSend_P(UFS_FORM_FILE_UPG, PSTR(D_SCRIPT_UPLOAD));
 
   WSContentSend_P(UFS_FORM_SDC_DIRa);
   if (ufs_type) {
@@ -516,7 +516,7 @@ void UfsListDir(char *path, uint8_t depth) {
   char name[32];
   char npath[128];
   char format[12];
-  sprintf(format, "%%-%ds", 24 - depth);
+  sprintf(format, PSTR("%%-%ds"), 24 - depth);
 
   File dir = dfsp->open(path, UFS_FILE_READ);
   if (dir) {
@@ -533,7 +533,7 @@ void UfsListDir(char *path, uint8_t depth) {
           break;
         }
       }
-      WSContentSend_P(UFS_FORM_SDC_DIRd, npath, path, "..");
+      WSContentSend_P(UFS_FORM_SDC_DIRd, npath, path, PSTR(".."));
     }
     char *ep;
     while (true) {
@@ -764,13 +764,13 @@ bool Xdrv50(uint8_t function) {
 #ifdef USE_WEBSERVER
     case FUNC_WEB_ADD_MANAGEMENT_BUTTON:
       if (ufs_type) {
-        WSContentSend_PD(UFS_WEB_DIR, D_MANAGE_FILE_SYSTEM);
+        WSContentSend_PD(UFS_WEB_DIR, PSTR(D_MANAGE_FILE_SYSTEM));
       }
       break;
     case FUNC_WEB_ADD_HANDLER:
-      Webserver->on("/ufsd", UfsDirectory);
-      Webserver->on("/ufsu", HTTP_GET, UfsDirectory);
-      Webserver->on("/ufsu", HTTP_POST,[](){Webserver->sendHeader("Location","/ufsu");Webserver->send(303);}, HandleUploadLoop);
+      Webserver->on(F("/ufsd"), UfsDirectory);
+      Webserver->on(F("/ufsu"), HTTP_GET, UfsDirectory);
+      Webserver->on(F("/ufsu"), HTTP_POST,[](){Webserver->sendHeader(F("Location"),F("/ufsu"));Webserver->send(303);}, HandleUploadLoop);
       break;
 #endif // USE_WEBSERVER
   }
diff --git a/tasmota/xsns_34_hx711.ino b/tasmota/xsns_34_hx711.ino
index 4f22d7cca..7dc9da3d7 100644
--- a/tasmota/xsns_34_hx711.ino
+++ b/tasmota/xsns_34_hx711.ino
@@ -241,7 +241,7 @@ bool HxCommand(void)
       break;
     case 7:  // WeightSave
       Settings.energy_frequency_calibration = Hx.weight;
-      Response_P(S_JSON_SENSOR_INDEX_SVALUE, XSNS_34, D_JSON_DONE);
+      Response_P(S_JSON_SENSOR_INDEX_SVALUE, XSNS_34, PSTR(D_JSON_DONE));
       break;
     case 8:  // Json on weight change
       if (strchr(XdrvMailbox.data, ',') != nullptr) {