How to fix viewer not loading

This guide helps you resolve issues when http://localhost:19741 shows a blank page, a connection error, or never finishes loading.

Prerequisites

The Live Set Viewer device is on a track in your Ableton session

Steps

Check that the device is on a track. The device must be actively loaded on a track in your session. If you removed it or the track is deleted, the server stops. Drag Live Set Viewer.amxd onto any track and try again.
Check the Max Console for the server message. Open the Max editor (double-click the device title bar) and go to Window > Max Console. Look for:
```
Live Set Viewer server listening on http://localhost:19741
```
If you do not see this message, the server did not start. Try removing the device from the track and adding it again.
Check that port 19741 is not in use. Another application may be using the same port. On macOS, open Terminal and run:
```
lsof -i :19741
```
On Windows, open Command Prompt and run:
```
netstat -ano | findstr :19741
```
If another process is using the port, quit that application and reload the device.
Try a different browser. Some browser extensions (particularly ad blockers or privacy tools) can interfere with WebSocket connections to localhost. Try opening http://localhost:19741 in a different browser or in a private/incognito window.
Restart Ableton Live. If none of the above resolved the issue, save your session, quit Ableton, and reopen it. The device will reinitialize on load.

If the page loads but shows an empty canvas with no tracks, the server is running but the initial data scan may have failed. See How to fix session not updating for next steps.