diff --git a/libraries/ESP8266HTTPClient/src/ESP8266HTTPClient.cpp b/libraries/ESP8266HTTPClient/src/ESP8266HTTPClient.cpp
index 61b9a8e4ff..a05b9dd6f0 100644
--- a/libraries/ESP8266HTTPClient/src/ESP8266HTTPClient.cpp
+++ b/libraries/ESP8266HTTPClient/src/ESP8266HTTPClient.cpp
@@ -113,8 +113,8 @@ class BearSSLTraits : public TransportTraits
  * constructor
  */
 HTTPClient::HTTPClient()
+    : _client(nullptr), _userAgent(F("ESP8266HTTPClient"))
 {
-    _client = nullptr;
 #if HTTPCLIENT_1_1_COMPATIBLE
     _tcpDeprecated.reset(nullptr);
 #endif
@@ -1294,21 +1294,21 @@ int HTTPClient::handleHeaderResponse()
                 String headerValue = headerLine.substring(headerLine.indexOf(':') + 1);
                 headerValue.trim();
 
-                if(headerName.equalsIgnoreCase("Content-Length")) {
+                if(headerName.equalsIgnoreCase(F("Content-Length"))) {
                     _size = headerValue.toInt();
                 }
 
-                if(_canReuse && headerName.equalsIgnoreCase("Connection")) {
+                if(_canReuse && headerName.equalsIgnoreCase(F("Connection"))) {
                     if(headerValue.indexOf("close") >= 0 && headerValue.indexOf("keep-alive") < 0) {
                         _canReuse = false;
                     }
                 }
 
-                if(headerName.equalsIgnoreCase("Transfer-Encoding")) {
+                if(headerName.equalsIgnoreCase(F("Transfer-Encoding"))) {
                     transferEncoding = headerValue;
                 }
 
-                if(headerName.equalsIgnoreCase("Location")) {
+                if(headerName.equalsIgnoreCase(F("Location"))) {
                     _location = headerValue;
                 }
 
@@ -1334,7 +1334,7 @@ int HTTPClient::handleHeaderResponse()
 
                 if(transferEncoding.length() > 0) {
                     DEBUG_HTTPCLIENT("[HTTP-Client][handleHeaderResponse] Transfer-Encoding: %s\n", transferEncoding.c_str());
-                    if(transferEncoding.equalsIgnoreCase("chunked")) {
+                    if(transferEncoding.equalsIgnoreCase(F("chunked"))) {
                         _transferEncoding = HTTPC_TE_CHUNKED;
                     } else {
                         return HTTPC_ERROR_ENCODING;
diff --git a/libraries/ESP8266HTTPClient/src/ESP8266HTTPClient.h b/libraries/ESP8266HTTPClient/src/ESP8266HTTPClient.h
index 189070a986..d6e4f88c0a 100644
--- a/libraries/ESP8266HTTPClient/src/ESP8266HTTPClient.h
+++ b/libraries/ESP8266HTTPClient/src/ESP8266HTTPClient.h
@@ -242,7 +242,7 @@ class HTTPClient
     String _uri;
     String _protocol;
     String _headers;
-    String _userAgent = "ESP8266HTTPClient";
+    String _userAgent;
     String _base64Authorization;
 
     /// Response handling
diff --git a/libraries/ESP8266WebServer/src/Parsing-impl.h b/libraries/ESP8266WebServer/src/Parsing-impl.h
index c6b8ea16e7..decc9c8e0b 100644
--- a/libraries/ESP8266WebServer/src/Parsing-impl.h
+++ b/libraries/ESP8266WebServer/src/Parsing-impl.h
@@ -238,7 +238,7 @@ bool ESP8266WebServerTemplate<ServerType>::_parseRequest(ClientType& client) {
       DEBUG_OUTPUT.println(headerValue);
 #endif
 
-      if (headerName.equalsIgnoreCase("Host")){
+      if (headerName.equalsIgnoreCase(F("Host"))){
         _hostHeader = headerValue;
       }
     }
diff --git a/libraries/ESP8266WiFi/src/ESP8266WiFi.cpp b/libraries/ESP8266WiFi/src/ESP8266WiFi.cpp
index 146c968a58..8f63a97fa6 100644
--- a/libraries/ESP8266WiFi/src/ESP8266WiFi.cpp
+++ b/libraries/ESP8266WiFi/src/ESP8266WiFi.cpp
@@ -49,24 +49,24 @@ extern "C" {
  * @param p Print interface
  */
 void ESP8266WiFiClass::printDiag(Print& p) {
-    const char* modes[] = { "NULL", "STA", "AP", "STA+AP" };
-    p.print("Mode: ");
+    const char* const modes[] = { "NULL", "STA", "AP", "STA+AP" };
+    p.print(F("Mode: "));
     p.println(modes[wifi_get_opmode()]);
 
-    const char* phymodes[] = { "", "B", "G", "N" };
-    p.print("PHY mode: ");
+    const char* const phymodes[] = { "", "B", "G", "N" };
+    p.print(F("PHY mode: "));
     p.println(phymodes[(int) wifi_get_phy_mode()]);
 
-    p.print("Channel: ");
+    p.print(F("Channel: "));
     p.println(wifi_get_channel());
 
-    p.print("AP id: ");
+    p.print(F("AP id: "));
     p.println(wifi_station_get_current_ap_id());
 
-    p.print("Status: ");
+    p.print(F("Status: "));
     p.println(wifi_station_get_connect_status());
 
-    p.print("Auto connect: ");
+    p.print(F("Auto connect: "));
     p.println(wifi_station_get_auto_connect());
 
     struct station_config conf;
@@ -75,22 +75,14 @@ void ESP8266WiFiClass::printDiag(Print& p) {
     char ssid[33]; //ssid can be up to 32chars, => plus null term
     memcpy(ssid, conf.ssid, sizeof(conf.ssid));
     ssid[32] = 0; //nullterm in case of 32 char ssid
- 
-    p.print("SSID (");
-    p.print(strlen(ssid));
-    p.print("): ");
-    p.println(ssid);
+    p.printf_P(PSTR("SSID (%d): %s\n"), strlen(ssid), ssid);
 
     char passphrase[65];
     memcpy(passphrase, conf.password, sizeof(conf.password));
     passphrase[64] = 0;
+    p.printf_P(PSTR("Passphrase (%d): %s\n"), strlen(passphrase), passphrase);
 
-    p.print("Passphrase (");
-    p.print(strlen(passphrase));
-    p.print("): ");
-    p.println(passphrase);
-
-    p.print("BSSID set: ");
+    p.print(F("BSSID set: "));
     p.println(conf.bssid_set);
 
 }