What causes a Unity WebGL out-of-memory error?

The WebGL build's memory heap exceeded what the browser tab allows — often an oversized initial heap, uncompressed textures, or memory that grows without being freed.

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 a Unity WebGL Build Running Out of Memory

Quick answer: Reduce the initial memory size and enable memory growth, compress textures and audio aggressively, strip unused assets and code, and avoid loading everything into RAM at once.

WebGL runs in a fixed memory sandbox, and Unity games are easy to push past it — especially on mobile browsers. The crash is an out-of-memory abort, not a code bug. Here is how to fit inside the budget.

How to fix it

1. Tune the memory settings

In Player Settings, WebGL, set a modest Initial Memory Size and enable Memory Growth so the heap starts small and expands only as needed. An oversized initial heap fails to allocate on low-memory devices before the game even starts.

2. Compress textures and audio

Textures dominate WebGL memory. Use Crunch or ASTC compression, drop max sizes, and atlas where possible. Compress audio and stream long clips instead of loading them whole.

3. Strip code and unused assets

Enable code stripping and IL2CPP, remove unreferenced assets, and split content into asset bundles loaded on demand. The less you load up front, the more headroom you keep.

4. Profile memory in the browser

Use the browser's memory tools and Unity's profiler over the network to find what grows. A steady climb means a leak — a reference holding assets that should have been unloaded.

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 Unity 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.

Reproduce it once with full context and the fix writes itself. The hunt is the expensive part.