diff --git a/html5/js/Client.js b/html5/js/Client.js
index bf847700..4f7f07f1 100644
--- a/html5/js/Client.js
+++ b/html5/js/Client.js
@@ -120,7 +120,7 @@ class XpraClient {
     this.PING_FREQUENCY = 5000;
     this.INFO_FREQUENCY = 1000;
     this.uuid = Utilities.getHexUUID();
-    this.offscreen_api = DECODE_WORKER && XpraOffscreenWorker.isAvailable();
+    this.offscreen_api = false;
     this.try_gpu = TRY_GPU_TRIGGER;
 
     this.init_encodings();
@@ -542,6 +542,7 @@ class XpraClient {
       this._do_connect(false);
       return;
     }
+    this.offscreen_api = DECODE_WORKER && XpraOffscreenWorker.isAvailable(this.ssl);
     this.clog("we have webworker support");
     // spawn worker that checks for a websocket
     const worker = new Worker("js/lib/wsworker_check.js");
diff --git a/html5/js/OffscreenDecodeWorkerHelper.js b/html5/js/OffscreenDecodeWorkerHelper.js
index 8ad75d4d..5f17f02d 100644
--- a/html5/js/OffscreenDecodeWorkerHelper.js
+++ b/html5/js/OffscreenDecodeWorkerHelper.js
@@ -33,16 +33,24 @@ const XpraOffscreenWorker = {
     return false;
   },
 
-  isAvailable() {
+  isAvailable(ssl) {
     if (Utilities.isSafari() && !this.isSafariVersionSupported()) {
+      console.log("offscreen canvas is not supported with this version of Safari");
       return false;
     }
 
     if (Utilities.isWebkit() && !Utilities.isChrome()) {
+      console.log("offscreen canvas is not supported with this webkit browser");
       return false;
     }
 
     if (Utilities.isFirefox() && this.isFirefoxVersionSupported()) {
+      console.log("offscreen canvas is not supported with this version of Firefox");
+      return false;
+    }
+
+    if (Utilities.isChrome() && !ssl) {
+      console.log("offscreen canvas requires https with Chrome");
       return false;
     }