diff --git a/cores/esp8266/WString.cpp b/cores/esp8266/WString.cpp
index bab537737e..7b9d9db934 100644
--- a/cores/esp8266/WString.cpp
+++ b/cores/esp8266/WString.cpp
@@ -156,9 +156,9 @@ unsigned char String::changeBuffer(unsigned int maxStrLen) {
     if (maxStrLen < sizeof(sso.buff) - 1) {
         if (isSSO() || !buffer()) {
             // Already using SSO, nothing to do
-	    uint16_t oldLen = len();
+            uint16_t oldLen = len();
             setSSO(true);
-	    setLen(oldLen);
+            setLen(oldLen);
             return 1;
         } else { // if bufptr && !isSSO()
             // Using bufptr, need to shrink into sso.buff
@@ -167,7 +167,7 @@ unsigned char String::changeBuffer(unsigned int maxStrLen) {
             free(wbuffer());
             uint16_t oldLen = len();
             setSSO(true);
-	    setLen(oldLen);
+            setLen(oldLen);
             memcpy(wbuffer(), temp, maxStrLen);
             return 1;
         }
@@ -204,7 +204,7 @@ unsigned char String::changeBuffer(unsigned int maxStrLen) {
 // /*********************************************/
 
 String & String::copy(const char *cstr, unsigned int length) {
-    if(!reserve(length)) {
+    if (!reserve(length)) {
         invalidate();
         return *this;
     }
@@ -225,11 +225,11 @@ String & String::copy(const __FlashStringHelper *pstr, unsigned int length) {
 
 #ifdef __GXX_EXPERIMENTAL_CXX0X__
 void String::move(String &rhs) {
-    if(buffer()) {
-        if(capacity() >= rhs.len()) {
+    if (buffer()) {
+        if (capacity() >= rhs.len()) {
             memmove_P(wbuffer(), rhs.buffer(), rhs.length() + 1);
             setLen(rhs.len());
-	    rhs.invalidate();
+            rhs.invalidate();
             return;
         } else {
             if (!isSSO()) {
@@ -255,10 +255,10 @@ void String::move(String &rhs) {
 #endif
 
 String & String::operator =(const String &rhs) {
-    if(this == &rhs)
+    if (this == &rhs)
         return *this;
 
-    if(rhs.buffer())
+    if (rhs.buffer())
         copy(rhs.buffer(), rhs.len());
     else
         invalidate();
@@ -268,20 +268,20 @@ String & String::operator =(const String &rhs) {
 
 #ifdef __GXX_EXPERIMENTAL_CXX0X__
 String & String::operator =(String &&rval) {
-    if(this != &rval)
+    if (this != &rval)
         move(rval);
     return *this;
 }
 
 String & String::operator =(StringSumHelper &&rval) {
-    if(this != &rval)
+    if (this != &rval)
         move(rval);
     return *this;
 }
 #endif
 
 String & String::operator =(const char *cstr) {
-    if(cstr)
+    if (cstr)
         copy(cstr, strlen(cstr));
     else
         invalidate();
@@ -323,11 +323,11 @@ unsigned char String::concat(const String &s) {
 
 unsigned char String::concat(const char *cstr, unsigned int length) {
     unsigned int newlen = len() + length;
-    if(!cstr)
+    if (!cstr)
         return 0;
-    if(length == 0)
+    if (length == 0)
         return 1;
-    if(!reserve(newlen))
+    if (!reserve(newlen))
         return 0;
     memmove_P(wbuffer() + len(), cstr, length + 1);
     setLen(newlen);
@@ -336,7 +336,7 @@ unsigned char String::concat(const char *cstr, unsigned int length) {
 }
 
 unsigned char String::concat(const char *cstr) {
-    if(!cstr)
+    if (!cstr)
         return 0;
     return concat(cstr, strlen(cstr));
 }
@@ -407,70 +407,70 @@ unsigned char String::concat(const __FlashStringHelper * str) {
 
 StringSumHelper & operator +(const StringSumHelper &lhs, const String &rhs) {
     StringSumHelper &a = const_cast<StringSumHelper&>(lhs);
-    if(!a.concat(rhs.buffer(), rhs.len()))
+    if (!a.concat(rhs.buffer(), rhs.len()))
         a.invalidate();
     return a;
 }
 
 StringSumHelper & operator +(const StringSumHelper &lhs, const char *cstr) {
     StringSumHelper &a = const_cast<StringSumHelper&>(lhs);
-    if(!cstr || !a.concat(cstr, strlen(cstr)))
+    if (!cstr || !a.concat(cstr, strlen(cstr)))
         a.invalidate();
     return a;
 }
 
 StringSumHelper & operator +(const StringSumHelper &lhs, char c) {
     StringSumHelper &a = const_cast<StringSumHelper&>(lhs);
-    if(!a.concat(c))
+    if (!a.concat(c))
         a.invalidate();
     return a;
 }
 
 StringSumHelper & operator +(const StringSumHelper &lhs, unsigned char num) {
     StringSumHelper &a = const_cast<StringSumHelper&>(lhs);
-    if(!a.concat(num))
+    if (!a.concat(num))
         a.invalidate();
     return a;
 }
 
 StringSumHelper & operator +(const StringSumHelper &lhs, int num) {
     StringSumHelper &a = const_cast<StringSumHelper&>(lhs);
-    if(!a.concat(num))
+    if (!a.concat(num))
         a.invalidate();
     return a;
 }
 
 StringSumHelper & operator +(const StringSumHelper &lhs, unsigned int num) {
     StringSumHelper &a = const_cast<StringSumHelper&>(lhs);
-    if(!a.concat(num))
+    if (!a.concat(num))
         a.invalidate();
     return a;
 }
 
 StringSumHelper & operator +(const StringSumHelper &lhs, long num) {
     StringSumHelper &a = const_cast<StringSumHelper&>(lhs);
-    if(!a.concat(num))
+    if (!a.concat(num))
         a.invalidate();
     return a;
 }
 
 StringSumHelper & operator +(const StringSumHelper &lhs, unsigned long num) {
     StringSumHelper &a = const_cast<StringSumHelper&>(lhs);
-    if(!a.concat(num))
+    if (!a.concat(num))
         a.invalidate();
     return a;
 }
 
 StringSumHelper & operator +(const StringSumHelper &lhs, float num) {
     StringSumHelper &a = const_cast<StringSumHelper&>(lhs);
-    if(!a.concat(num))
+    if (!a.concat(num))
         a.invalidate();
     return a;
 }
 
 StringSumHelper & operator +(const StringSumHelper &lhs, double num) {
     StringSumHelper &a = const_cast<StringSumHelper&>(lhs);
-    if(!a.concat(num))
+    if (!a.concat(num))
         a.invalidate();
     return a;
 }
@@ -503,9 +503,9 @@ unsigned char String::equals(const String &s2) const {
 }
 
 unsigned char String::equals(const char *cstr) const {
-    if(len() == 0)
+    if (len() == 0)
         return (cstr == NULL || *cstr == 0);
-    if(cstr == NULL)
+    if (cstr == NULL)
         return buffer()[0] == 0;
     return strcmp(buffer(), cstr) == 0;
 }
@@ -527,16 +527,16 @@ unsigned char String::operator>=(const String &rhs) const {
 }
 
 unsigned char String::equalsIgnoreCase(const String &s2) const {
-    if(this == &s2)
+    if (this == &s2)
         return 1;
-    if(len() != s2.len())
+    if (len() != s2.len())
         return 0;
-    if(len() == 0)
+    if (len() == 0)
         return 1;
     const char *p1 = buffer();
     const char *p2 = s2.buffer();
-    while(*p1) {
-        if(tolower(*p1++) != tolower(*p2++))
+    while (*p1) {
+        if (tolower(*p1++) != tolower(*p2++))
             return 0;
     }
     return 1;
@@ -545,18 +545,18 @@ unsigned char String::equalsIgnoreCase(const String &s2) const {
 unsigned char String::equalsConstantTime(const String &s2) const {
     // To avoid possible time-based attacks present function
     // compares given strings in a constant time.
-    if(len() != s2.len())
+    if (len() != s2.len())
         return 0;
     //at this point lengths are the same
-    if(len() == 0)
+    if (len() == 0)
         return 1;
     //at this point lenghts are the same and non-zero
     const char *p1 = buffer();
     const char *p2 = s2.buffer();
     unsigned int equalchars = 0;
     unsigned int diffchars = 0;
-    while(*p1) {
-        if(*p1 == *p2)
+    while (*p1) {
+        if (*p1 == *p2)
             ++equalchars;
         else
             ++diffchars;
@@ -596,13 +596,13 @@ char String::charAt(unsigned int loc) const {
 }
 
 void String::setCharAt(unsigned int loc, char c) {
-    if(loc < len())
+    if (loc < len())
         wbuffer()[loc] = c;
 }
 
 char & String::operator[](unsigned int index) {
     static char dummy_writable_char;
-    if(index >= len() || !buffer()) {
+    if (index >= len() || !buffer()) {
         dummy_writable_char = 0;
         return dummy_writable_char;
     }
@@ -610,20 +610,20 @@ char & String::operator[](unsigned int index) {
 }
 
 char String::operator[](unsigned int index) const {
-    if(index >= len() || !buffer())
+    if (index >= len() || !buffer())
         return 0;
     return buffer()[index];
 }
 
 void String::getBytes(unsigned char *buf, unsigned int bufsize, unsigned int index) const {
-    if(!bufsize || !buf)
+    if (!bufsize || !buf)
         return;
-    if(index >= len()) {
+    if (index >= len()) {
         buf[0] = 0;
         return;
     }
     unsigned int n = bufsize - 1;
-    if(n > len() - index)
+    if (n > len() - index)
         n = len() - index;
     strncpy((char *) buf, buffer() + index, n);
     buf[n] = 0;
@@ -638,10 +638,10 @@ int String::indexOf(char c) const {
 }
 
 int String::indexOf(char ch, unsigned int fromIndex) const {
-    if(fromIndex >= len())
+    if (fromIndex >= len())
         return -1;
     const char* temp = strchr(buffer() + fromIndex, ch);
-    if(temp == NULL)
+    if (temp == NULL)
         return -1;
     return temp - buffer();
 }
@@ -651,10 +651,10 @@ int String::indexOf(const String &s2) const {
 }
 
 int String::indexOf(const String &s2, unsigned int fromIndex) const {
-    if(fromIndex >= len())
+    if (fromIndex >= len())
         return -1;
     const char *found = strstr(buffer() + fromIndex, s2.buffer());
-    if(found == NULL)
+    if (found == NULL)
         return -1;
     return found - buffer();
 }
@@ -664,13 +664,13 @@ int String::lastIndexOf(char theChar) const {
 }
 
 int String::lastIndexOf(char ch, unsigned int fromIndex) const {
-    if(fromIndex >= len())
+    if (fromIndex >= len())
         return -1;
     char tempchar = buffer()[fromIndex + 1];
     wbuffer()[fromIndex + 1] = '\0';
     char* temp = strrchr(wbuffer(), ch);
     wbuffer()[fromIndex + 1] = tempchar;
-    if(temp == NULL)
+    if (temp == NULL)
         return -1;
     return temp - buffer();
 }
@@ -680,31 +680,31 @@ int String::lastIndexOf(const String &s2) const {
 }
 
 int String::lastIndexOf(const String &s2, unsigned int fromIndex) const {
-    if(s2.len() == 0 || len() == 0 || s2.len() > len())
+    if (s2.len() == 0 || len() == 0 || s2.len() > len())
         return -1;
-    if(fromIndex >= len())
+    if (fromIndex >= len())
         fromIndex = len() - 1;
     int found = -1;
-    for(char *p = wbuffer(); p <= wbuffer() + fromIndex; p++) {
+    for (char *p = wbuffer(); p <= wbuffer() + fromIndex; p++) {
         p = strstr(p, s2.buffer());
-        if(!p)
+        if (!p)
             break;
-        if((unsigned int) (p - wbuffer()) <= fromIndex)
+        if ((unsigned int) (p - wbuffer()) <= fromIndex)
             found = p - buffer();
     }
     return found;
 }
 
 String String::substring(unsigned int left, unsigned int right) const {
-    if(left > right) {
+    if (left > right) {
         unsigned int temp = right;
         right = left;
         left = temp;
     }
     String out;
-    if(left >= len())
+    if (left >= len())
         return out;
-    if(right > len())
+    if (right > len())
         right = len();
     char temp = buffer()[right];  // save the replaced character
     wbuffer()[right] = '\0';
@@ -718,28 +718,28 @@ String String::substring(unsigned int left, unsigned int right) const {
 // /*********************************************/
 
 void String::replace(char find, char replace) {
-    if(!buffer())
+    if (!buffer())
         return;
-    for(char *p = wbuffer(); *p; p++) {
-        if(*p == find)
+    for (char *p = wbuffer(); *p; p++) {
+        if (*p == find)
             *p = replace;
     }
 }
 
 void String::replace(const String& find, const String& replace) {
-    if(len() == 0 || find.len() == 0)
+    if (len() == 0 || find.len() == 0)
         return;
     int diff = replace.len() - find.len();
     char *readFrom = wbuffer();
     char *foundAt;
-    if(diff == 0) {
-        while((foundAt = strstr(readFrom, find.buffer())) != NULL) {
+    if (diff == 0) {
+        while ((foundAt = strstr(readFrom, find.buffer())) != NULL) {
             memmove_P(foundAt, replace.buffer(), replace.len());
             readFrom = foundAt + replace.len();
         }
-    } else if(diff < 0) {
+    } else if (diff < 0) {
         char *writeTo = wbuffer();
-        while((foundAt = strstr(readFrom, find.buffer())) != NULL) {
+        while ((foundAt = strstr(readFrom, find.buffer())) != NULL) {
             unsigned int n = foundAt - readFrom;
             memmove_P(writeTo, readFrom, n);
             writeTo += n;
@@ -751,19 +751,19 @@ void String::replace(const String& find, const String& replace) {
         memmove_P(writeTo, readFrom, strlen(readFrom)+1);
     } else {
         unsigned int size = len(); // compute size needed for result
-        while((foundAt = strstr(readFrom, find.buffer())) != NULL) {
+        while ((foundAt = strstr(readFrom, find.buffer())) != NULL) {
             readFrom = foundAt + find.len();
             size += diff;
         }
-        if(size == len())
+        if (size == len())
             return;
-        if(size > capacity() && !changeBuffer(size))
+        if (size > capacity() && !changeBuffer(size))
             return; // XXX: tell user!
         int index = len() - 1;
-        while(index >= 0 && (index = lastIndexOf(find, index)) >= 0) {
+        while (index >= 0 && (index = lastIndexOf(find, index)) >= 0) {
             readFrom = wbuffer() + index + find.len();
             memmove_P(readFrom + diff, readFrom, len() - (readFrom - buffer()));
-	    int newLen = len() + diff;
+            int newLen = len() + diff;
             memmove_P(wbuffer() + index, replace.buffer(), replace.len());
             setLen(newLen);
             wbuffer()[newLen] = 0;
@@ -780,13 +780,13 @@ void String::remove(unsigned int index) {
 }
 
 void String::remove(unsigned int index, unsigned int count) {
-    if(index >= len()) {
+    if (index >= len()) {
         return;
     }
-    if(count <= 0) {
+    if (count <= 0) {
         return;
     }
-    if(count > len() - index) {
+    if (count > len() - index) {
         count = len() - index;
     }
     char *writeTo = wbuffer() + index;
@@ -797,33 +797,33 @@ void String::remove(unsigned int index, unsigned int count) {
 }
 
 void String::toLowerCase(void) {
-    if(!buffer())
+    if (!buffer())
         return;
-    for(char *p = wbuffer(); *p; p++) {
+    for (char *p = wbuffer(); *p; p++) {
         *p = tolower(*p);
     }
 }
 
 void String::toUpperCase(void) {
-    if(!buffer())
+    if (!buffer())
         return;
-    for(char *p = wbuffer(); *p; p++) {
+    for (char *p = wbuffer(); *p; p++) {
         *p = toupper(*p);
     }
 }
 
 void String::trim(void) {
-    if(!buffer() || len() == 0)
+    if (!buffer() || len() == 0)
         return;
     char *begin = wbuffer();
-    while(isspace(*begin))
+    while (isspace(*begin))
         begin++;
     char *end = wbuffer() + len() - 1;
-    while(isspace(*end) && end >= begin)
+    while (isspace(*end) && end >= begin)
         end--;
     unsigned int newlen = end + 1 - begin;
     setLen(newlen);
-    if(begin > buffer())
+    if (begin > buffer())
         memmove_P(wbuffer(), begin, newlen);
     wbuffer()[newlen] = 0;
 }
diff --git a/doc/PROGMEM.rst b/doc/PROGMEM.rst
index 2b8138f6a8..e455df639d 100644
--- a/doc/PROGMEM.rst
+++ b/doc/PROGMEM.rst
@@ -145,7 +145,7 @@ constructor:
 
 .. code:: cpp
 
-    String(const char *cstr = ""); // constructor from const char * 
+    String(const char *cstr = nullptr); // constructor from const char *
     String(const String &str); // copy constructor
     String(const __FlashStringHelper *str); // constructor for flash strings 
 
diff --git a/libraries/ArduinoOTA/ArduinoOTA.cpp b/libraries/ArduinoOTA/ArduinoOTA.cpp
index 57fcd6fad7..0b07894743 100644
--- a/libraries/ArduinoOTA/ArduinoOTA.cpp
+++ b/libraries/ArduinoOTA/ArduinoOTA.cpp
@@ -168,7 +168,7 @@ int ArduinoOTAClass::parseInt(){
 }
 
 String ArduinoOTAClass::readStringUntil(char end){
-  String res = "";
+  String res;
   int value;
   while(true){
     value = _udp_ota->read();
diff --git a/libraries/DNSServer/src/DNSServer.cpp b/libraries/DNSServer/src/DNSServer.cpp
index 31d2c90792..2113ae0f5b 100644
--- a/libraries/DNSServer/src/DNSServer.cpp
+++ b/libraries/DNSServer/src/DNSServer.cpp
@@ -119,7 +119,7 @@ void DNSServer::respondToRequest(uint8_t *buffer, size_t length)
 			  query, queryLength);
 
   // If we have no domain name configured, just return an error
-  if (_domainName == "")
+  if (_domainName.isEmpty())
     return replyWithError(dnsHeader, _errorReplyCode,
 			  query, queryLength);
 
diff --git a/libraries/ESP8266HTTPClient/src/ESP8266HTTPClient.cpp b/libraries/ESP8266HTTPClient/src/ESP8266HTTPClient.cpp
index ad54b506d9..c7a8a5259b 100644
--- a/libraries/ESP8266HTTPClient/src/ESP8266HTTPClient.cpp
+++ b/libraries/ESP8266HTTPClient/src/ESP8266HTTPClient.cpp
@@ -137,9 +137,9 @@ void HTTPClient::clear()
 {
     _returnCode = 0;
     _size = -1;
-    _headers = "";
+    _headers.clear();
+    _location.clear();
     _payload.reset();
-    _location = "";
 }
 
 
@@ -657,7 +657,7 @@ int HTTPClient::sendRequest(const char * type, const uint8_t * payload, size_t s
         // wipe out any existing headers from previous request
         for(size_t i = 0; i < _headerKeysCount; i++) {
             if (_currentHeaders[i].value.length() > 0) {
-                _currentHeaders[i].value = "";
+                _currentHeaders[i].value.clear();
             }
         }
 
diff --git a/libraries/ESP8266HTTPUpdateServer/src/ESP8266HTTPUpdateServer-impl.h b/libraries/ESP8266HTTPUpdateServer/src/ESP8266HTTPUpdateServer-impl.h
index 190a597066..8af0750192 100644
--- a/libraries/ESP8266HTTPUpdateServer/src/ESP8266HTTPUpdateServer-impl.h
+++ b/libraries/ESP8266HTTPUpdateServer/src/ESP8266HTTPUpdateServer-impl.h
@@ -77,7 +77,7 @@ void ESP8266HTTPUpdateServerTemplate<ServerType>::setup(ESP8266WebServerTemplate
       HTTPUpload& upload = _server->upload();
 
       if(upload.status == UPLOAD_FILE_START){
-        _updaterError = String();
+        _updaterError.clear();
         if (_serial_output)
           Serial.setDebugOutput(true);
 
diff --git a/libraries/ESP8266WebServer/examples/FSBrowser/FSBrowser.ino b/libraries/ESP8266WebServer/examples/FSBrowser/FSBrowser.ino
index 69065c43d5..fb5847d4b0 100644
--- a/libraries/ESP8266WebServer/examples/FSBrowser/FSBrowser.ino
+++ b/libraries/ESP8266WebServer/examples/FSBrowser/FSBrowser.ino
@@ -122,7 +122,7 @@ void handleFileUpload() {
     }
     DBG_OUTPUT_PORT.print("handleFileUpload Name: "); DBG_OUTPUT_PORT.println(filename);
     fsUploadFile = filesystem->open(filename, "w");
-    filename = String();
+    filename.clear();
   } else if (upload.status == UPLOAD_FILE_WRITE) {
     //DBG_OUTPUT_PORT.print("handleFileUpload Data: "); DBG_OUTPUT_PORT.println(upload.currentSize);
     if (fsUploadFile) {
@@ -150,7 +150,7 @@ void handleFileDelete() {
   }
   filesystem->remove(path);
   server.send(200, "text/plain", "");
-  path = String();
+  path.clear();
 }
 
 void handleFileCreate() {
@@ -172,7 +172,7 @@ void handleFileCreate() {
     return server.send(500, "text/plain", "CREATE FAILED");
   }
   server.send(200, "text/plain", "");
-  path = String();
+  path.clear();
 }
 
 void handleFileList() {
@@ -184,7 +184,7 @@ void handleFileList() {
   String path = server.arg("dir");
   DBG_OUTPUT_PORT.println("handleFileList: " + path);
   Dir dir = filesystem->openDir(path);
-  path = String();
+  path.clear();
 
   String output = "[";
   while (dir.next()) {
@@ -275,13 +275,13 @@ void setup(void) {
 
   //get heap status, analog input value and all GPIO statuses in one json call
   server.on("/all", HTTP_GET, []() {
-    String json = "{";
+    String json('{');
     json += "\"heap\":" + String(ESP.getFreeHeap());
     json += ", \"analog\":" + String(analogRead(A0));
     json += ", \"gpio\":" + String((uint32_t)(((GPI | GPO) & 0xFFFF) | ((GP16I & 0x01) << 16)));
     json += "}";
     server.send(200, "text/json", json);
-    json = String();
+    json.clear();
   });
   server.begin();
   DBG_OUTPUT_PORT.println("HTTP server started");
diff --git a/libraries/ESP8266WebServer/examples/SDWebServer/SDWebServer.ino b/libraries/ESP8266WebServer/examples/SDWebServer/SDWebServer.ino
index efe0207746..1679b5806a 100644
--- a/libraries/ESP8266WebServer/examples/SDWebServer/SDWebServer.ino
+++ b/libraries/ESP8266WebServer/examples/SDWebServer/SDWebServer.ino
@@ -209,7 +209,7 @@ void printDirectory() {
     return returnFail("BAD PATH");
   }
   File dir = SD.open((char *)path.c_str());
-  path = String();
+  path.clear();
   if (!dir.isDirectory()) {
     dir.close();
     return returnFail("NOT DIR");
diff --git a/libraries/ESP8266WebServer/src/Parsing-impl.h b/libraries/ESP8266WebServer/src/Parsing-impl.h
index decc9c8e0b..54bcd6c28e 100644
--- a/libraries/ESP8266WebServer/src/Parsing-impl.h
+++ b/libraries/ESP8266WebServer/src/Parsing-impl.h
@@ -89,7 +89,7 @@ bool ESP8266WebServerTemplate<ServerType>::_parseRequest(ClientType& client) {
   String url = req.substring(addr_start + 1, addr_end);
   String versionEnd = req.substring(addr_end + 8);
   _currentVersion = atoi(versionEnd.c_str());
-  String searchStr = "";
+  String searchStr;
   int hasSearch = url.indexOf('?');
   if (hasSearch != -1){
     searchStr = url.substring(hasSearch + 1);
@@ -144,7 +144,7 @@ bool ESP8266WebServerTemplate<ServerType>::_parseRequest(ClientType& client) {
     while(1){
       req = client.readStringUntil('\r');
       client.readStringUntil('\n');
-      if (req == "") break;//no moar headers
+      if (req.isEmpty()) break;//no moar headers
       int headerDiv = req.indexOf(':');
       if (headerDiv == -1){
         break;
@@ -222,7 +222,7 @@ bool ESP8266WebServerTemplate<ServerType>::_parseRequest(ClientType& client) {
     while(1){
       req = client.readStringUntil('\r');
       client.readStringUntil('\n');
-      if (req == "") break;//no moar headers
+      if (req.isEmpty()) break;//no moar headers
       int headerDiv = req.indexOf(':');
       if (headerDiv == -1){
         break;
@@ -452,7 +452,7 @@ bool ESP8266WebServerTemplate<ServerType>::_parseForm(ClientType& client, const
               line = client.readStringUntil('\r');
               client.readStringUntil('\n');
               if (line.startsWith("--"+boundary)) break;
-              if (argValue.length() > 0) argValue += "\n";
+              if (argValue.length() > 0) argValue += '\n';
               argValue += line;
             }
 #ifdef DEBUG_ESP_HTTP_SERVER
@@ -600,7 +600,7 @@ bool ESP8266WebServerTemplate<ServerType>::_parseForm(ClientType& client, const
 template <typename ServerType>
 String ESP8266WebServerTemplate<ServerType>::urlDecode(const String& text)
 {
-  String decoded = "";
+  String decoded;
   char temp[] = "0x00";
   unsigned int len = text.length();
   unsigned int i = 0;
diff --git a/libraries/ESP8266WiFiMesh/src/ESP8266WiFiMesh.cpp b/libraries/ESP8266WiFiMesh/src/ESP8266WiFiMesh.cpp
index c3fb4774db..e35cac33b9 100644
--- a/libraries/ESP8266WiFiMesh/src/ESP8266WiFiMesh.cpp
+++ b/libraries/ESP8266WiFiMesh/src/ESP8266WiFiMesh.cpp
@@ -31,7 +31,7 @@
 const IPAddress ESP8266WiFiMesh::emptyIP = IPAddress();
 const uint32_t ESP8266WiFiMesh::lwipVersion203Signature[3] {2,0,3};
 
-String ESP8266WiFiMesh::lastSSID = "";
+String ESP8266WiFiMesh::lastSSID;
 bool ESP8266WiFiMesh::staticIPActivated = false;
 
 // IP needs to be at the same subnet as server gateway (192.168.4 in this case). Station gateway ip must match ip for server.
@@ -55,7 +55,7 @@ ESP8266WiFiMesh::ESP8266WiFiMesh(ESP8266WiFiMesh::requestHandlerType requestHand
 {
   storeLwipVersion();
   
-  updateNetworkNames(meshName, (nodeID != "" ? nodeID : uint64ToString(ESP.getChipId())));
+  updateNetworkNames(meshName, (!nodeID.isEmpty() ? nodeID : uint64ToString(ESP.getChipId())));
   _requestHandler = requestHandler;
   _responseHandler = responseHandler;
   setWiFiChannel(meshWiFiChannel);
@@ -67,9 +67,9 @@ ESP8266WiFiMesh::ESP8266WiFiMesh(ESP8266WiFiMesh::requestHandlerType requestHand
 
 void ESP8266WiFiMesh::updateNetworkNames(const String &newMeshName, const String &newNodeID)
 {
-  if(newMeshName != "")
+  if(!newMeshName.isEmpty())
     _meshName = newMeshName;
-  if(newNodeID != "")
+  if(!newNodeID.isEmpty())
     _nodeID = newNodeID;
 
   String newSSID = _meshName + _nodeID;
@@ -453,7 +453,7 @@ void ESP8266WiFiMesh::initiateConnectionToAP(const String &targetSSID, int targe
  */
 transmission_status_t ESP8266WiFiMesh::connectToNode(const String &targetSSID, int targetChannel, uint8_t *targetBSSID)
 {
-  if(staticIPActivated && lastSSID != "" && lastSSID != targetSSID) // So we only do this once per connection, in case there is a performance impact.
+  if(staticIPActivated && !lastSSID.isEmpty() && lastSSID != targetSSID) // So we only do this once per connection, in case there is a performance impact.
   {
     #ifdef ENABLE_STATIC_IP_OPTIMIZATION
     if(atLeastLwipVersion(lwipVersion203Signature))
@@ -562,12 +562,12 @@ void ESP8266WiFiMesh::attemptTransmission(const String &message, bool concluding
       WiFi.disconnect();
       yield();
 
-      String currentSSID = "";
+      String currentSSID;
       int currentWiFiChannel = NETWORK_INFO_DEFAULT_INT;
       uint8_t *currentBSSID = NULL;
 
       // If an SSID has been assigned, it is prioritized over an assigned networkIndex since the networkIndex is more likely to change.
-      if(currentNetwork.SSID != "")
+      if(!currentNetwork.SSID.isEmpty())
       {
         currentSSID = currentNetwork.SSID;
         currentWiFiChannel = currentNetwork.wifiChannel;
diff --git a/tests/device/test_WiFi_events/test_WiFi_events.ino b/tests/device/test_WiFi_events/test_WiFi_events.ino
index 88777b61ab..e5a4079ffb 100644
--- a/tests/device/test_WiFi_events/test_WiFi_events.ino
+++ b/tests/device/test_WiFi_events/test_WiFi_events.ino
@@ -95,7 +95,7 @@ TEST_CASE("STA mode events are called both when using DHCP and static config", "
     delay(100);
 
     REQUIRE(events == "connected,got_ip,disconnected,");
-    events = String();
+    events.clear();
 
     // now run the same with static IP config saved above