What causes JSON parsing errors in GameMaker?

The text is not valid JSON — hand-edited config files with trailing commas or comments, server responses returning HTML error pages, encoding issues, or empty files from interrupted writes.

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 json_parse Errors and Invalid JSON Handling in GameMaker

Quick answer: Wrap parsing in try/catch, validate the payload shape after parsing, and treat every external JSON source (files, HTTP) as untrusted input.

Modern GML's json_parse throws on invalid input — unhandled, that is a crash from a config typo or a 500 error page. The wrapper pattern makes it survivable. Here it is.

How to fix it

1. Parse inside try/catch

try { data = json_parse(txt); } catch (e) { /* log e.message, use defaults */ } — parsing anything that came from disk or network without a catch is a shipped crash.

2. Check the shape after parse

Valid JSON is not necessarily your JSON — verify expected keys exist (variable_struct_exists) and types match before reading deep paths.

3. Suspect the HTTP layer

APIs return HTML error pages and empty bodies under failure; check the async event's status and a content sanity peek (first character { or [) before parsing.

4. Report the bad payload

On parse failure in the wild, capture a truncated copy of the offending text with the error — 'invalid JSON from settings.json' with the actual content is instantly fixable.

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.

The errors you never hear about are the ones quietly costing you players. Visibility turns them into a worklist.