What causes garbage collection spikes from LINQ in Update in Unity?

LINQ methods allocate enumerators, delegates, and intermediate collections every call, and running them each frame floods the heap until the GC stalls the main thread.

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 Garbage Collection Spikes From LINQ in Update in Unity

Quick answer: Replace LINQ in hot paths with plain for loops, cache results that do not change every frame, and avoid closures that capture variables.

Your game micro-stutters at a regular interval, which is the garbage collector reclaiming the allocations your per-frame LINQ produces. Hot paths must not allocate. Here is how to remove the garbage.

How to fix it

1. Replace LINQ with loops

A Where().Select().ToList() in Update allocates several objects every frame. Rewrite it as a single explicit for loop that mutates a reused list, so the per-frame allocation drops to zero.

2. Cache invariant results

If a query's result only changes when data changes, compute it once on change instead of every frame. Re-deriving the same filtered set 60 times a second is pure waste.

3. Avoid capturing closures

Lambdas that capture local variables allocate a closure object on each call. Use static methods or precomputed predicates, and profile with the Profiler's GC Alloc column to confirm the hot path is clean.

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 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.

Ship the fix, watch the signature disappear from the next build. That's how you know it's really gone.