diff --git a/wled00/data/settings_sync.htm b/wled00/data/settings_sync.htm
index 8dff78dc..52c55ae5 100644
--- a/wled00/data/settings_sync.htm
+++ b/wled00/data/settings_sync.htm
@@ -1,18 +1,44 @@
 <!DOCTYPE html>
 <html lang="en"><head><meta name="viewport" content="width=500"><meta charset="utf-8"><title>Sync Settings</title>
 <script>var d=document;
+function gId(s)
+{
+  return d.getElementById(s);
+}
 function H(){window.open("https://github.com/Aircoookie/WLED/wiki/Settings#sync-settings");}function B(){window.open("/settings","_self");}
 function adj(){if (d.Sf.DI.value == 6454) {if (d.Sf.DA.value == 1) d.Sf.DA.value = 0; if (d.Sf.EU.value == 1) d.Sf.EU.value = 0;}
                else if (d.Sf.DI.value == 5568) {if (d.Sf.DA.value == 0) d.Sf.DA.value = 1; if (d.Sf.EU.value == 0) d.Sf.EU.value = 1;} }
-function SP(){var p = d.Sf.DI.value; d.getElementById("xp").style.display = (p > 0)?"none":"block"; if (p > 0) d.Sf.EP.value = p;}
-function SetVal(){switch(parseInt(d.Sf.EP.value)){case 5568: d.Sf.DI.value = 5568; break; case 6454: d.Sf.DI.value = 6454; break; case 4048: d.Sf.DI.value = 4048; break; }; SP();}
+function FC()
+{
+  for(j=0;j<8;j++)
+  {
+    gId("G"+(j+1)).checked=gId("GS").value>>j&1;
+    gId("R"+(j+1)).checked=gId("GR").value>>j&1;
+  }
+}
+function GC()
+{
+  var a=0, b=0;
+
+  var m=1;
+  for(j=0;j<8;j++)
+  {
+    a+=gId("G"+(j+1)).checked*m;
+    b+=gId("R"+(j+1)).checked*m;
+    m*=2;
+  }
+  gId("GS").value=a;
+  gId("GR").value=b;
+}
+function SP(){var p = d.Sf.DI.value; gId("xp").style.display = (p > 0)?"none":"block"; if (p > 0) d.Sf.EP.value = p;}
+function SetVal(){switch(parseInt(d.Sf.EP.value)){case 5568: d.Sf.DI.value = 5568; break; case 6454: d.Sf.DI.value = 6454; break; case 4048: d.Sf.DI.value = 4048; break; }; SP();FC();}
 function S(){GetV();SetVal();}
 function GetV(){var d=document;}
 </script>
 <style>@import url("/style.css");</style>
 </head>
 <body onload="S()">
-<form id="form_s" name="Sf" method="post">
+<form id="form_s" name="Sf" method="post" onsubmit="GC()">
 <div class="toprow">
 <div class="helpB"><button type="button" onclick="H()">?</button></div>
 <button type="button" onclick="B()">Back</button><button type="submit">Save</button><hr>
@@ -21,6 +47,8 @@ function GetV(){var d=document;}
 <h3>WLED Broadcast</h3>
 UDP Port: <input name="UP" type="number" min="1" max="65535" class="d5" required><br>
 2nd Port: <input name="U2" type="number" min="1" max="65535" class="d5" required><br><br>
+<input name="GS" id="GS" type="number" style="display: none;"> <!-- hidden inputs for bitwise group checkboxes -->
+<input name="GR" id="GR" type="number" style="display: none;">
 <table style="margin: 0 auto;">
     <tr>
         <td>Sync groups</td>
diff --git a/wled00/html_settings.h b/wled00/html_settings.h
index 472c7a14..1b6b8277 100644
--- a/wled00/html_settings.h
+++ b/wled00/html_settings.h
@@ -238,30 +238,32 @@ type="button" onclick="Save()">Save</button></form></body></html>)=====";
 // Autogenerated from wled00/data/settings_sync.htm, do not edit!!
 const char PAGE_settings_sync[] PROGMEM = R"=====(<!DOCTYPE html><html lang="en"><head><meta name="viewport" content="width=500">
 <meta charset="utf-8"><title>Sync Settings</title><script>
-var d=document;function H(){window.open("https://github.com/Aircoookie/WLED/wiki/Settings#sync-settings")}function B(){window.open("/settings","_self")}function adj(){6454==d.Sf.DI.value?(1==d.Sf.DA.value&&(d.Sf.DA.value=0),1==d.Sf.EU.value&&(d.Sf.EU.value=0)):5568==d.Sf.DI.value&&(0==d.Sf.DA.value&&(d.Sf.DA.value=1),0==d.Sf.EU.value&&(d.Sf.EU.value=1))}function SP(){var e=d.Sf.DI.value;d.getElementById("xp").style.display=e>0?"none":"block",e>0&&(d.Sf.EP.value=e)}function SetVal(){switch(parseInt(d.Sf.EP.value)){case 5568:d.Sf.DI.value=5568;break;case 6454:d.Sf.DI.value=6454;break;case 4048:d.Sf.DI.value=4048}SP()}function S(){GetV(),SetVal()}function GetV() {
+var d=document;function gId(e){return d.getElementById(e)}function H(){window.open("https://github.com/Aircoookie/WLED/wiki/Settings#sync-settings")}function B(){window.open("/settings","_self")}function adj(){6454==d.Sf.DI.value?(1==d.Sf.DA.value&&(d.Sf.DA.value=0),1==d.Sf.EU.value&&(d.Sf.EU.value=0)):5568==d.Sf.DI.value&&(0==d.Sf.DA.value&&(d.Sf.DA.value=1),0==d.Sf.EU.value&&(d.Sf.EU.value=1))}function FC(){for(j=0;j<8;j++)gId("G"+(j+1)).checked=gId("GS").value>>j&1,gId("R"+(j+1)).checked=gId("GR").value>>j&1}function GC(){var e=0,d=0,n=1;for(j=0;j<8;j++)e+=gId("G"+(j+1)).checked*n,d+=gId("R"+(j+1)).checked*n,n*=2;gId("GS").value=e,gId("GR").value=d}function SP(){var e=d.Sf.DI.value;gId("xp").style.display=e>0?"none":"block",e>0&&(d.Sf.EP.value=e)}function SetVal(){switch(parseInt(d.Sf.EP.value)){case 5568:d.Sf.DI.value=5568;break;case 6454:d.Sf.DI.value=6454;break;case 4048:d.Sf.DI.value=4048}SP(),FC()}function S(){GetV(),SetVal()}function GetV() {
 %CSS%%SCSS%</head><body onload="S()">
-<form id="form_s" name="Sf" method="post"><div class="toprow"><div 
-class="helpB"><button type="button" onclick="H()">?</button></div><button 
+<form id="form_s" name="Sf" method="post" onsubmit="GC()"><div class="toprow">
+<div class="helpB"><button type="button" onclick="H()">?</button></div><button 
 type="button" onclick="B()">Back</button><button type="submit">Save</button><hr>
 </div><h2>Sync setup</h2><h3>WLED Broadcast</h3>UDP Port: <input name="UP" 
 type="number" min="1" max="65535" class="d5" required><br>2nd Port: <input 
-name="U2" type="number" min="1" max="65535" class="d5" required><br><br><table 
-style="margin:0 auto"><tr><td>Sync groups</td><td>1</td><td>2</td><td>3</td><td>
-4</td><td>5</td><td>6</td><td>7</td><td>8</td></tr><tr><td>Send:</td><td><input 
-type="checkbox" id="G1" name="G1"></td><td><input type="checkbox" id="G2" 
-name="G2"></td><td><input type="checkbox" id="G3" name="G3"></td><td><input 
-type="checkbox" id="G4" name="G4"></td><td><input type="checkbox" id="G5" 
-name="G5"></td><td><input type="checkbox" id="G6" name="G6"></td><td><input 
-type="checkbox" id="G7" name="G7"></td><td><input type="checkbox" id="G8" 
-name="G8"></td></tr><tr><td>Receive:</td><td><input type="checkbox" id="R1" 
-name="R1"></td><td><input type="checkbox" id="R2" name="R2"></td><td><input 
-type="checkbox" id="R3" name="R3"></td><td><input type="checkbox" id="R4" 
-name="R4"></td><td><input type="checkbox" id="R5" name="R5"></td><td><input 
-type="checkbox" id="R6" name="R6"></td><td><input type="checkbox" id="R7" 
-name="R7"></td><td><input type="checkbox" id="R8" name="R8"></td></tr></table>
-<br>Receive: <input type="checkbox" name="RB">Brightness, <input 
-type="checkbox" name="RC">Color, and <input type="checkbox" name="RX">Effects
-<br>Send notifications on direct change: <input type="checkbox" name="SD"><br>
+name="U2" type="number" min="1" max="65535" class="d5" required><br><br><input 
+name="GS" id="GS" type="number" style="display:none"> <input name="GR" id="GR" 
+type="number" style="display:none"><table style="margin:0 auto"><tr><td>
+Sync groups</td><td>1</td><td>2</td><td>3</td><td>4</td><td>5</td><td>6</td><td>
+7</td><td>8</td></tr><tr><td>Send:</td><td><input type="checkbox" id="G1" 
+name="G1"></td><td><input type="checkbox" id="G2" name="G2"></td><td><input 
+type="checkbox" id="G3" name="G3"></td><td><input type="checkbox" id="G4" 
+name="G4"></td><td><input type="checkbox" id="G5" name="G5"></td><td><input 
+type="checkbox" id="G6" name="G6"></td><td><input type="checkbox" id="G7" 
+name="G7"></td><td><input type="checkbox" id="G8" name="G8"></td></tr><tr><td>
+Receive:</td><td><input type="checkbox" id="R1" name="R1"></td><td><input 
+type="checkbox" id="R2" name="R2"></td><td><input type="checkbox" id="R3" 
+name="R3"></td><td><input type="checkbox" id="R4" name="R4"></td><td><input 
+type="checkbox" id="R5" name="R5"></td><td><input type="checkbox" id="R6" 
+name="R6"></td><td><input type="checkbox" id="R7" name="R7"></td><td><input 
+type="checkbox" id="R8" name="R8"></td></tr></table><br>Receive: <input 
+type="checkbox" name="RB">Brightness, <input type="checkbox" name="RC">
+Color, and <input type="checkbox" name="RX">Effects<br>
+Send notifications on direct change: <input type="checkbox" name="SD"><br>
 Send notifications on button press or IR: <input type="checkbox" name="SB"><br>
 Send Alexa notifications: <input type="checkbox" name="SA"><br>
 Send Philips Hue change notifications: <input type="checkbox" name="SH"><br>
diff --git a/wled00/set.cpp b/wled00/set.cpp
index a12979d9..99579122 100644
--- a/wled00/set.cpp
+++ b/wled00/set.cpp
@@ -209,13 +209,8 @@ void handleSettingsSet(AsyncWebServerRequest *request, byte subPage)
     t = request->arg(F("U2")).toInt();
     if (t > 0) udpPort2 = t;
 
-    char k[3]; k[2] = 0;
-    syncGroups = receiveGroups = 0;
-    for (uint8_t i=0; i<8; i++) {
-      k[1] = 49+i;  // char '1','2',...
-      k[0] = 'G';    syncGroups |= request->hasArg(k)<<i;
-      k[0] = 'R'; receiveGroups |= request->hasArg(k)<<i;
-    }
+    syncGroups = request->arg(F("GS")).toInt();
+    receiveGroups = request->arg(F("GR")).toInt();
 
     receiveNotificationBrightness = request->hasArg(F("RB"));
     receiveNotificationColor = request->hasArg(F("RC"));
diff --git a/wled00/udp.cpp b/wled00/udp.cpp
index aa565c46..c0af11ce 100644
--- a/wled00/udp.cpp
+++ b/wled00/udp.cpp
@@ -11,6 +11,7 @@
 void notify(byte callMode, bool followUp)
 {
   if (!udpConnected) return;
+  if (!syncGroups) return;
   switch (callMode)
   {
     case CALL_MODE_INIT:          return;
@@ -75,7 +76,7 @@ void notify(byte callMode, bool followUp)
   udpOut[35] = (ms >> 0) & 0xFF;
 
   //sync groups
-  udpOut[36] = syncGroups & 0xFF;
+  udpOut[36] = syncGroups;
   
   IPAddress broadcastIp;
   broadcastIp = ~uint32_t(Network.subnetMask()) | uint32_t(Network.gatewayIP());
@@ -229,7 +230,10 @@ void handleNotifications()
     byte version = udpIn[11];
 
     // if we are not part of any sync group ignore message
-    if (version > 8 && !(receiveGroups & udpIn[36])) return;
+    if (version < 9 || version > 199) {
+      // legacy senders are treated as if sending in sync group 1 only
+      if (!(receiveGroups & 0x01)) return;
+    } else if (!(receiveGroups & udpIn[36])) return;
     
     bool someSel = (receiveNotificationBrightness || receiveNotificationColor || receiveNotificationEffects);
     //apply colors from notification
@@ -274,7 +278,7 @@ void handleNotifications()
     }
 
     //adjust system time, but only if sender is more accurate than self
-    if (version > 7)
+    if (version > 7 && version < 200)
     {
       Toki::Time tm;
       tm.sec = (udpIn[30] << 24) | (udpIn[31] << 16) | (udpIn[32] << 8) | (udpIn[33]);
diff --git a/wled00/xml.cpp b/wled00/xml.cpp
index c6273c15..a0ab50fa 100644
--- a/wled00/xml.cpp
+++ b/wled00/xml.cpp
@@ -429,14 +429,9 @@ void getSettingsJS(byte subPage, char* dest)
   {
     sappend('v',SET_F("UP"),udpPort);
     sappend('v',SET_F("U2"),udpPort2);
+    sappend('v',SET_F("GS"),syncGroups);
+    sappend('v',SET_F("GR"),receiveGroups);
 
-    char k[3]; k[2] = 0;
-    for (int i = 0; i<8; i++)
-    {
-      k[1] = 49+i; //ascii 1,2,3,...
-      k[0] = 'G'; sappend('c',k,(syncGroups>>i)&0x01);
-      k[0] = 'R'; sappend('c',k,(receiveGroups>>i)&0x01);
-    }
     sappend('c',SET_F("HX"),liveHSVCorrection);
     sappend('v',SET_F("HS"),liveHSVSaturation);
     sappend('v',SET_F("HV"),liveHSVValue);
