Why does my game slow down the longer I play?

Most likely a memory leak or thermal throttling. A leak means memory grows over the session, slowing the game and causing more frequent garbage-collection stutters as it accumulates. Thermal throttling means the device heats up under sustained load and reduces performance to cool down, degrading frame rate over time (common on mobile). Both build gradually, so a quick test shows fine performance and the slowdown only appears in longer sessions.

How do I tell if it's a memory leak or thermal throttling?

Look at memory and thermal behavior over a session. If memory climbs continuously over time, that points at a memory leak (and you'd trace what's accumulating). If performance drops while memory stays roughly stable, especially on mobile after sustained play, that points at thermal throttling (and you'd reduce sustained CPU/GPU load). Capturing long-session performance and memory data distinguishes them, since each has a different fix, and both are invisible in short tests.

What Causes Performance to Degrade Over a Session?

Q: What causes performance to degrade over a session?

Performance that worsens the longer a session runs usually has one of two causes: a memory leak (growing memory usage that slows the game and triggers more frequent garbage-collection stutters) or thermal throttling (the device heating up under sustained load until it reduces CPU/GPU performance to cool down). Memory fragmentation and accumulating state can also contribute. All build gradually over time, which is why the degradation appears only after a while of playing.

Quick answer: Performance degrading over a session usually has one of two causes: a memory leak (growing memory slowing the game and triggering more GC) or thermal throttling (the device heating up and reducing performance). Both build over time.

When a game runs fine at first but gets slower the longer you play, that degradation-over-time has specific causes that only manifest in longer sessions. Here's what causes performance to degrade over a session.

The Two Main Causes

Performance that worsens over a session, rather than being consistently low, points at something that accumulates or builds over time. Two causes dominate:

Memory leaks, memory that grows over the session, which slows the game (more memory pressure) and triggers more frequent garbage collection (causing more frequent stutters)
Thermal throttling, the device heating up under sustained load until it reduces CPU/GPU performance to cool down, degrading frame rate over time
Memory fragmentation, memory becoming fragmented over time, making allocation slower
Accumulating state, growing data structures or unbounded systems that get slower as they fill

Memory leaks and thermal throttling are by far the most common, both build gradually, which is why the degradation appears only after a while.

Why It Only Appears in Longer Sessions

Both leaks and thermal throttling need time to manifest, a leak accumulates over minutes, and a device heats up over ten or twenty minutes of play. So a quick test shows fine performance, and the degradation only hits players in longer sessions, escaping testing entirely.

Bugnet captures performance and memory-related crashes over full real sessions, so degradation that only appears after minutes of play, from leaks or throttling, surfaces in your data. Capturing long-session behavior is essential because session-degradation is invisible in short tests.

Diagnosing the Cause

To tell which cause you have, look at memory and thermal behavior over a session. Memory climbing over time points at a leak; performance dropping while memory is stable points at thermal throttling (especially on mobile). Capturing the long-session data distinguishes them, and each has its own fix (fix the leak; reduce sustained load).

Bugnet captures the long-session performance and memory data needed to tell them apart. So performance degrading over a session is usually a memory leak or thermal throttling, and diagnosing it means capturing long-session behavior to see which is building over time.

Performance degrading over a session is usually a memory leak (growing memory, more GC) or thermal throttling (device heating up). Both build over time and only show in longer sessions. Capture long-session data to tell them apart.