diff --git a/esphome/components/web_server_idf/multipart_parser.cpp b/esphome/components/web_server_idf/multipart_parser.cpp
index 0eb7db6a8c..5d6cd6f1ad 100644
--- a/esphome/components/web_server_idf/multipart_parser.cpp
+++ b/esphome/components/web_server_idf/multipart_parser.cpp
@@ -13,7 +13,6 @@ static const char *const TAG = "multipart_parser";
 static constexpr size_t CRLF_LENGTH = 2;
 static constexpr size_t MIN_BOUNDARY_BUFFER = 4;  // Extra bytes to keep for split boundary detection
 static constexpr const char *CRLF_STR = "\r\n";
-static constexpr const char *DOUBLE_DASH = "--";
 
 bool MultipartParser::parse(const uint8_t *data, size_t len) {
   // Append new data to buffer
diff --git a/esphome/components/web_server_idf/multipart_parser.h b/esphome/components/web_server_idf/multipart_parser.h
index 466bfd6dd4..c0a36f95e9 100644
--- a/esphome/components/web_server_idf/multipart_parser.h
+++ b/esphome/components/web_server_idf/multipart_parser.h
@@ -12,6 +12,8 @@ namespace web_server_idf {
 // Multipart form data parser for ESP-IDF
 class MultipartParser {
  public:
+  static constexpr const char *MULTIPART_BOUNDARY_PREFIX = "--";
+
   enum State : uint8_t { BOUNDARY_SEARCH, HEADERS, CONTENT, DONE, ERROR };
 
   struct Part {
@@ -23,7 +25,7 @@ class MultipartParser {
   };
 
   explicit MultipartParser(const std::string &boundary)
-      : boundary_("--" + boundary),
+      : boundary_(MULTIPART_BOUNDARY_PREFIX + boundary),
         state_(BOUNDARY_SEARCH),
         content_start_(0),
         content_length_(0),