Every time you travel between the Overworld, Nether, and End, your client creates a new ClientWorld. The old world should be garbage-collected, but several popular mods accidentally hold references to it - causing it to stay in memory forever.

After just a few dimension changes, this can eat 4-8 GB of RAM, leading to lag spikes, stuttering, and eventually crashes.

Dimension Leak Fix automatically detects dimension transitions and surgically breaks these retention chains, recovering 2-4 GB of memory per transition.

What it fixes

Source	Problem	Impact
Entity references	Entities in the old world hold a `.level` field pointing back to it	~200 MB per transition
Collective	`BlockEntityData.cachedBlockEntities` retains old worlds through nested WeakHashMaps	~1.2 GB per transition
AmbientSounds	AirPocketScanner thread holds thousands of ChunkSections as a GC root	~1.4 GB per transition
Create	Renderer caches hold references to old world data	Variable
Chunk storage	Old world's ChunkManager retains all loaded chunks in memory	~1-3 GB per transition

How it works

The mod uses a two-phase approach:

Phase A (instant): When you change dimension, the mod immediately detaches entity references, flushes Collective caches, stops the AmbientSounds scanner thread, detaches Spark command senders, and invalidates Create's renderer.
Phase B (3 seconds later): The mod clears the old world's chunk storage array and entity sets. This is delayed to avoid interfering with the renderer during the transition.

Compatibility

Client-side only - does not need to be installed on the server
Works with or without any of the mods listed above - the mod detects what's installed and only applies relevant fixes
Tested with 200+ mods including Iris, Sodium, Distant Horizons, Create, Collective, AmbientSounds

Log output

The mod logs everything it does. Example output after a dimension change:

[DimensionLeakFix] Dimension change detected, cleaning up old world...
[DimensionLeakFix]   Entities: 131 world references detached
[DimensionLeakFix]   Collective: 1 cache(s) flushed in cachedBlockEntities
[DimensionLeakFix]   AmbientSounds: scanner stopped (3 fields cleared)
[DimensionLeakFix]   Create: renderer cache invalidated
[DimensionLeakFix] Phase A complete (137 operations)
[DimensionLeakFix] Phase B scheduled (3s delay)
[DimensionLeakFix] Phase B: releasing old world data...
[DimensionLeakFix]   Chunks: 2809 slots released
[DimensionLeakFix]   loadedChunks: 2809 entries cleared
[DimensionLeakFix] Phase B complete (2810 references released, ~3706 MB freed)

Used in the Legends Reborn: Medieval modpack.