How to Catch Unhandled GML Exceptions With exception_unhandled_handler in GameMaker

GML gives you one global hook that turns every would-be crash box into a structured report. Shipping without it means debugging from screenshots. Here is the setup.

How to fix it

1. Register the handler at boot

In your first-run script: exception_unhandled_handler(handle_crash); where the function receives the exception struct — message, longMessage, script, line, and stacktrace fields.

2. Attach the context that matters

Send the exception plus build version, OS, room name, and a breadcrumb ring buffer of recent actions — the difference between 'null in scr_enemy line 12' and an actually reproducible report.

3. Choose the aftermath deliberately

Return a value to continue (risky mid-corruption) or clean up and exit with an apologetic dialog — for most games, save-what-is-safe then exit beats continuing in unknown state.

4. Watch the dashboard, not the inbox

With the handler feeding error tracking, crash frequency per version replaces anecdote — you will find your top crash is something no player ever wrote in about.

Catching the ones you can't reproduce

The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.

Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.

This is where a tool like Bugnet earns its place. Its SDK captures every GameMaker error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.