How to Fix Frame Rate Stutter from Garbage Collection in Unity

A game that is smooth most of the time but hitches on a rhythm is almost always garbage collection. Something allocates every frame, the heap fills, and the collector stops the world to clean up. Here is how to confirm and fix it.

How to fix it

1. Confirm it in the Profiler

Open the Profiler, record gameplay, and look for GC Alloc per frame and spikes in the CPU track that coincide with the hitch. If garbage collection lines up with the stutter, allocations are your target.

2. Stop allocating every frame

Cache arrays, lists, and StringBuilders instead of creating them in Update. Avoid string concatenation, LINQ, and foreach over some collections in hot paths — each allocates. Reuse buffers rather than newing them up.

3. Avoid boxing and hidden allocations

Passing a struct where an object is expected boxes it onto the heap. Watch for delegates, closures, and enum-keyed dictionaries that allocate. The Profiler's GC Alloc column points at the exact call.

4. Enable the incremental garbage collector

In Player Settings, turn on Incremental GC so collection is spread across frames instead of one long stop. It softens the hitch while you reduce the allocations causing 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 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.