Why does AssetBundle.LoadFromFile freeze the main thread for 200ms?

LZMA decompresses on the main thread. Switch to LZ4 (much faster decode) and use LoadFromFileAsync. LZ4 also supports streaming reads.

LZ4 ~10-20% larger files but decompresses 5-10x faster. Worth the size for runtime smoothness; LZMA is for download size where decompression budget exists (server-side, not runtime).

BuildAssetBundleOptions.ChunkBasedCompression for LZ4. Default is LZMA. Rebuild bundles to apply.

Fix: AssetBundle Load Causes 200ms Hitches

Quick answer: Build with BuildAssetBundleOptions.ChunkBasedCompression (LZ4). Use LoadFromFileAsync at runtime.

Open inventory loads a bundle. 200ms freeze. LZMA decompression on main thread blocks rendering.

The Fix

// Build
BuildPipeline.BuildAssetBundles(
    outputPath, builds,
    BuildAssetBundleOptions.ChunkBasedCompression,   // LZ4
    BuildTarget.StandaloneWindows64);

// Runtime
var req = AssetBundle.LoadFromFileAsync(path);
yield return req;
var bundle = req.assetBundle;

var assetReq = bundle.LoadAssetAsync<GameObject>("item.prefab");
yield return assetReq;
Instantiate(assetReq.asset);

LZ4 decompresses in chunks, streaming. Async APIs hand work to a background thread. No main-thread freeze.

Verifying

Profiler: AssetBundle.LoadFromFile time on worker thread; main thread frame time stable. Visible hitch gone.

“LZ4 build. Async load. No freeze.”

Related Issues

For AssetBundle dedup, see dedup. For Addressables update, see content update.

LZ4. Async. Smooth.