diff --git a/tools/cdata.js b/tools/cdata.js
index c569a6f2aa..759d24c2da 100644
--- a/tools/cdata.js
+++ b/tools/cdata.js
@@ -38,6 +38,11 @@ const wledBanner = `
 \t\t\x1b[36m build script for web UI
 \x1b[0m`;
 
+// Generate build timestamp as UNIX timestamp (seconds since epoch)
+function generateBuildTime() {
+  return Math.floor(Date.now() / 1000);
+}
+
 const singleHeader = `/*
  * Binary array for the Web UI.
  * gzip is used for smaller size and improved speeds.
@@ -45,6 +50,9 @@ const singleHeader = `/*
  * Please see https://kno.wled.ge/advanced/custom-features/#changing-web-ui
  * to find out how to easily modify the web UI source!
  */
+
+// Automatically generated build time for cache busting (UNIX timestamp)
+#define WEB_BUILD_TIME ${generateBuildTime()}
  
 `;
 
diff --git a/wled00/wled_server.cpp b/wled00/wled_server.cpp
index d899d3113b..09aeaccff2 100644
--- a/wled00/wled_server.cpp
+++ b/wled00/wled_server.cpp
@@ -67,7 +67,7 @@ static bool inLocalSubnet(const IPAddress &client) {
  */
 
 static void generateEtag(char *etag, uint16_t eTagSuffix) {
-  sprintf_P(etag, PSTR("%7d-%02x-%04x"), VERSION, cacheInvalidate, eTagSuffix);
+  sprintf_P(etag, PSTR("%u-%02x-%04x"), WEB_BUILD_TIME, cacheInvalidate, eTagSuffix);
 }
 
 static void setStaticContentCacheHeaders(AsyncWebServerResponse *response, int code, uint16_t eTagSuffix = 0) {