What causes files that load in the Godot editor but not in the exported build?

The file was never packed into the export — non-resource files (.txt, .json, .csv) are excluded unless added to the export filters, or the code builds paths that only exist in the project folder.

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 “Cannot open file 'res://…'” Errors in an Exported Godot Game

Quick answer: Add the file patterns to the export preset's include filters, load data through FileAccess with res:// paths, and verify by listing the PCK contents or testing the export early.

Everything works in the editor because the editor reads your project folder; the export only packs recognized resources plus whatever filters you add. Your JSON and text data are the casualties. Here is the fix.

How to fix it

1. Add include filters

In the export preset, set Resources > Filters to export non-resource files to patterns like *.json, *.csv, *.txt — subfolders included.

2. Load via res:// and FileAccess

Use FileAccess.open("res://data/items.json", FileAccess.READ); OS file paths that happen to work in the editor will not exist inside a PCK.

3. Write to user://, never res://

The packed filesystem is read-only; saves, logs, and downloads belong under user://.

4. Smoke-test the export

Export and run a build that touches every data file at startup in CI or before each release — this failure class is invisible until someone runs the shipped game.

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 Godot 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.