Add the option to add multiple headers with the same name

README.md

@@ -577,13 +577,13 @@ request->multipart();     // bool:    True if the request has content type "mult
 int headers = request->headers();
 int i;
 for(i=0;i<headers;i++){
-  AsyncWebHeader* h = request->getHeader(i);
+  const AsyncWebHeader* h = request->getHeader(i);
   Serial.printf("HEADER[%s]: %s\n", h->name().c_str(), h->value().c_str());
 }
 
 //get specific header by name
 if(request->hasHeader("MyHeader")){
-  AsyncWebHeader* h = request->getHeader("MyHeader");
+  const AsyncWebHeader* h = request->getHeader("MyHeader");
   Serial.printf("MyHeader: %s\n", h->value().c_str());
 }
 

examples/Headers/Headers.ino

@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// Copyright 2016-2025 Hristo Gochkov, Mathieu Carbou, Emil Muratov
+
+//
+// Query and send headers
+//
+
+#include <Arduino.h>
+#ifdef ESP32
+#include <AsyncTCP.h>
+#include <WiFi.h>
+#elif defined(ESP8266)
+#include <ESP8266WiFi.h>
+#include <ESPAsyncTCP.h>
+#elif defined(TARGET_RP2040)
+#include <WebServer.h>
+#include <WiFi.h>
+#endif
+
+#include <ESPAsyncWebServer.h>
+
+static AsyncWebServer server(80);
+
+void setup() {
+  Serial.begin(115200);
+
+#ifndef CONFIG_IDF_TARGET_ESP32H2
+  WiFi.mode(WIFI_AP);
+  WiFi.softAP("esp-captive");
+#endif
+
+  //
+  // curl -v http://192.168.4.1
+  //
+  server.on("/", HTTP_GET, [](AsyncWebServerRequest *request) {
+    //List all collected headers
+    int headers = request->headers();
+    int i;
+    for (i = 0; i < headers; i++) {
+      const AsyncWebHeader *h = request->getHeader(i);
+      Serial.printf("HEADER[%s]: %s\n", h->name().c_str(), h->value().c_str());
+    }
+
+    AsyncWebServerResponse *response = request->beginResponse(200, "text/plain", "Hello World!");
+
+    //Add header to the response
+    response->addHeader("Server", "ESP Async Web Server");
+
+    //Add multiple headers with the same name
+    response->addHeader("Set-Cookie", "sessionId=38afes7a8", false);
+    response->addHeader("Set-Cookie", "id=a3fWa; Max-Age=2592000", false);
+    response->addHeader("Set-Cookie", "qwerty=219ffwef9w0f; Domain=example.com", false);
+
+    //Remove specific header
+    response->removeHeader("Set-Cookie", "sessionId=38afes7a8");
+
+    //Remove all headers with the same name
+    response->removeHeader("Set-Cookie");
+
+    request->send(response);
+  });
+
+  server.begin();
+}
+
+void loop() {
+  //Sleep in the loop task to not keep the CPU busy
+  delay(1000);
+}

src/ESPAsyncWebServer.h

@@ -953,6 +953,8 @@ class AsyncWebServerResponse {
   size_t _writtenLength;
   WebResponseState _state;
 
+  static bool headerMustBePresentOnce(const String &name);
+
 public:
   static const char *responseCodeToString(int code);
 
@@ -979,6 +981,7 @@ class AsyncWebServerResponse {
     return addHeader(name.c_str(), value, replaceExisting);
   }
   bool removeHeader(const char *name);
+  bool removeHeader(const char *name, const char *value);
   const AsyncWebHeader *getHeader(const char *name) const;
   const std::list<AsyncWebHeader> &getHeaders() const {
     return _headers;

src/WebResponses.cpp

@@ -96,8 +96,21 @@ void AsyncWebServerResponse::setContentType(const char *type) {
 }
 
 bool AsyncWebServerResponse::removeHeader(const char *name) {
-  for (auto i = _headers.begin(); i != _headers.end(); ++i) {
+  bool h_erased = false;
+  for (auto i = _headers.begin(); i != _headers.end();) {
     if (i->name().equalsIgnoreCase(name)) {
+      _headers.erase(i);
+      h_erased = true;
+    } else {
+      ++i;
+    }
+  }
+  return h_erased;
+}
+
+bool AsyncWebServerResponse::removeHeader(const char *name, const char *value) {
+  for (auto i = _headers.begin(); i != _headers.end(); ++i) {
+    if (i->name().equalsIgnoreCase(name) && i->value().equalsIgnoreCase(value)) {
       _headers.erase(i);
       return true;
     }
@@ -112,6 +125,15 @@ const AsyncWebHeader *AsyncWebServerResponse::getHeader(const char *name) const
   return (iter == std::end(_headers)) ? nullptr : &(*iter);
 }
 
+bool AsyncWebServerResponse::headerMustBePresentOnce(const String &name) {
+  for (uint8_t i = 0; i < T_only_once_headers_len; i++) {
+    if (name.equalsIgnoreCase(T_only_once_headers[i])) {
+      return true;
+    }
+  }
+  return false;
+}
+
 bool AsyncWebServerResponse::addHeader(const char *name, const char *value, bool replaceExisting) {
   for (auto i = _headers.begin(); i != _headers.end(); ++i) {
     if (i->name().equalsIgnoreCase(name)) {
@@ -120,9 +142,11 @@ bool AsyncWebServerResponse::addHeader(const char *name, const char *value, bool
         // remove, break and add the new one
         _headers.erase(i);
         break;
-      } else {
+      } else if (headerMustBePresentOnce(i->name())) {  // we can have only one header with that name
         // do not update
         return false;
+      } else {
+        break;  // accept multiple headers with the same name
       }
     }
   }

src/literals.h

@@ -28,6 +28,7 @@ static constexpr const char *T_Content_Disposition = "content-disposition";
 static constexpr const char *T_Content_Encoding = "content-encoding";
 static constexpr const char *T_Content_Length = "content-length";
 static constexpr const char *T_Content_Type = "content-type";
+static constexpr const char *T_Content_Location = "content-location";
 static constexpr const char *T_Cookie = "cookie";
 static constexpr const char *T_CORS_ACAC = "access-control-allow-credentials";
 static constexpr const char *T_CORS_ACAH = "access-control-allow-headers";
@@ -36,6 +37,7 @@ static constexpr const char *T_CORS_ACAO = "access-control-allow-origin";
 static constexpr const char *T_CORS_ACMA = "access-control-max-age";
 static constexpr const char *T_CORS_O = "origin";
 static constexpr const char *T_data_ = "data: ";
+static constexpr const char *T_Date = "date";
 static constexpr const char *T_DIGEST = "digest";
 static constexpr const char *T_DIGEST_ = "digest ";
 static constexpr const char *T_ETag = "etag";
@@ -71,6 +73,7 @@ static constexpr const char *T_retry_after = "retry-after";
 static constexpr const char *T_nn = "\n\n";
 static constexpr const char *T_rn = "\r\n";
 static constexpr const char *T_rnrn = "\r\n\r\n";
+static constexpr const char *T_Server = "server";
 static constexpr const char *T_Transfer_Encoding = "transfer-encoding";
 static constexpr const char *T_TRUE = "true";
 static constexpr const char *T_UPGRADE = "upgrade";
@@ -183,4 +186,8 @@ static constexpr const char *T_HTTP_CODE_504 = "Gateway Time-out";
 static constexpr const char *T_HTTP_CODE_505 = "HTTP Version not supported";
 static constexpr const char *T_HTTP_CODE_ANY = "Unknown code";
 
+static constexpr const uint8_t T_only_once_headers_len = 11;
+static constexpr const char *T_only_once_headers[] = {T_Content_Length,    T_Content_Type,     T_Date,   T_ETag,    T_Last_Modified, T_LOCATION, T_retry_after,
+                                                      T_Transfer_Encoding, T_Content_Location, T_Server, T_WWW_AUTH};
+
 }  // namespace asyncsrv