Unpacking AssetBundles — Extracting Unity Assets with AssetStudio

1. What AssetBundle Unpacking Is

An AssetBundle is Unity’s asset packaging format: a game’s models, textures, audio and other assets are all packed into it. Unpacking means extracting those packaged assets back out in reverse, to look at exactly what is inside.

In a build pipeline, AssetBundle unpacking has several very practical uses:

• Analysing build output: after a build finishes, unpacking the AssetBundles lets you check which assets were actually packed in, confirming that they went into the right bundles.
• Hunting down duplicate assets: different AssetBundles may reference the same texture or the same material; after unpacking, comparing the asset lists of each bundle reveals the redundancy, and you can shrink the bundle size.
• Checking for missing assets: when an asset you expected in some AssetBundle is not there, or a reference is broken, unpacking lets you quickly tell whether it is a build configuration problem or an asset dependency problem.
• Verifying asset compression: after unpacking, look at the size, format and compression ratio of the textures and compare them with the originals to judge whether the compression meets your targets.
• Extracting and reusing assets: export models, textures, audio and so on out of the AssetBundle, for study or for building up your own asset collection.

AssetStudio is the most popular open-source Unity asset extraction tool today. Developed by Perfare and now maintained by zhangjiequan, it supports parsing AssetBundles from Unity 3.x through 2022.3.x.

Project page: zhangjiequan/AssetStudio

2. Download and Install

Download the latest version from the GitHub Releases page (currently v0.16.53):

• AssetStudio.net472.zip — requires .NET Framework 4.7.2
• AssetStudio.net6.zip — requires .NET Desktop Runtime 6.0

Unzip it and run AssetStudioGUI.exe directly; no installation is needed.

3. Loading AssetBundle Files

There are two ways to load them:

Loading Directly

File → Load file to pick a single file, or File → Load folder to load an entire folder. This approach decompresses the AssetBundle into memory to read it, and may consume a fair amount of memory when handling large files.

Extract First, Then Load (Recommended)

First use File → Extract file or Extract folder to extract the AssetBundle into a folder, then load from there. This approach saves memory, and is recommended when handling large AssetBundles.

1. File → Extract folder → select the directory containing the AssetBundle → select the output directory
2. File → Load folder → select the output directory from the previous step

Once loading is finished, the left-hand panel shows the asset tree, categorised by type: Texture2D, AudioClip, Mesh, Font, TextAsset, Shader, MonoBehaviour and so on.

4. Exporting Assets

Select an asset in the asset list, then right-click and choose Export to export it. The supported export formats are as follows:

Batch export: hold Ctrl to select several assets, then right-click Export.

5. Exporting Models and Animations

AssetStudio supports exporting 3D models together with their animations:

• Exporting a static model: select the model in the “Scene Hierarchy” panel and use the Model menu to export it as FBX or OBJ.
• Exporting a model with animations: select the model in “Scene Hierarchy”, then hold Ctrl in the “Asset List” to select several AnimationClips, and use Model → Export selected objects with AnimationClip.
• Exporting an animator controller: select the Animator in the “Asset List” and export it via the Export menu; the related animations are bound automatically.

6. Handling IL2CPP Projects

For Unity projects compiled with IL2CPP, an extra step is required:

1. First use Il2CppDumper to dump global-metadata.dat and GameAssembly.dll, producing dummy DLL files.
2. The first time you select a MonoBehaviour-type asset in AssetStudio, point it at the folder containing the dummy DLLs.
3. After that you can view and export the script data normally.

7. Common Questions

Q: Loading an AssetBundle says the version is unsupported?

A: Set the SpecifyUnityVersion property manually in AssetsManager.cs to specify the Unity version, then recompile.

Q: The extracted textures are blurry?

A: Check the texture format option in the export settings, and prefer the lossless PNG format.

Q: The model has no materials after export?

A: Tick the Export Materials option when exporting.

8. Summary

AssetStudio is a sharp tool for Unity asset extraction, with comprehensive features. Extract first and then load to save memory, and pair it with Il2CppDumper when handling IL2CPP projects.

A small step forward every day is a new height!