What causes permission errors during GameMaker Windows builds?

The build could not write its output — a previous instance of the game (or the runner) still holds files, antivirus locks freshly written executables, OneDrive-synced project folders lock files mid-write, or the output path needs elevation.

How do I catch this when it only happens for some players?

Capture it automatically from the player's device with the full stack trace, the device and OS, the build, and a breadcrumb trail of what they did. That turns a vague complaint into a specific, reproducible issue you can fix without owning the hardware it happens on.

How to Fix “Permission Error : unable to open file” GameMaker Build Failures

Quick answer: Kill lingering game/runner processes, exclude project and cache folders from antivirus and cloud sync, and keep projects out of protected or synced directories.

Igor fails the build when Windows will not let it replace its own outputs — something is holding or scanning the file. The holders are a short list. Here it is.

How to fix it

1. Close the previous run

A crashed or backgrounded copy of your game keeps the exe locked; check Task Manager for the game and runner processes and kill them before rebuilding.

2. Exclude from real-time AV scanning

Antivirus scanning each just-written build artifact causes intermittent locks — exclude the project folder, the GameMaker cache, and the temp output directories.

3. Move out of OneDrive/Dropbox

Sync clients lock files while uploading, colliding with rapid rebuilds — keep projects in a plain local folder and back up via version control instead.

4. Clean the cache when stuck

Press the broom (clean) to clear stale locked intermediates, and reboot if a phantom handle survives — then address which holder caused it.

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.

Most of the time the fix is small. Seeing the failure clearly is the part that actually costs you.