When you create a build of your Unity project, the Data folder (or equivalent on target platforms) contains the serialized files that make up the content of your application. The primary files in the build’s Data folder related to asset loading are:
globalgamemanager: Contains core engine data, global project settings (like Quality Settings, Graphics Settings Physics settings, Tags, and Layers).globalgamemanager.assets: Contains assets referenced from the globalgamemanager file. This can include ScriptableObjects, such as HDRP or URP settings, and other assets referenced from those settings.resources.assets: Contains all assets located within any folder named Resources in your project. These assets are always included in the build, regardless of whether they’re directly referenced by any scene, and can be loaded with Resources.Load.level files appended with a number, for example, level0, level1: Each level file corresponds to the Scene List in Build Profiles, in the order they appear. These files contain GameObjects and components specific to that scene.sharedassets files appended with a number, for example, sharedassets0, sharedassets1: These files contain assets referenced by a scene reference. Their numbering corresponds to the scene in the scene build order that references them first.Resources/unity_builtin_extra : Contains built-in shaders if they’re referenced by the build.Resources/unity default resources: Contains built-in assets that are always included in the build, such as default materials and fonts. This file is pre-built for each target platform, and distributed as part of the Unity Editor installation. Unity copies the file into the output as part of the build process.Important: The exact layout and file formats that Unity uses might change between versions, so don’t write code that depends on the specific naming convention for the output files.
Each serialized file in the build can be accompanied by a .resS file which contains texture or mesh data. For example level0 might be accompanied by level0.resS and sharedassets0 might be accompanied by sharedassets0.assets.resS.`
Similarly any serialized file that contains AudioClip or VideoClip objects will have an accompanying .resource file that contains the binary data for those objects. For example level0.resource or sharedassets1.resource.
Unity stores the binary data in separate files to reduce memory usage when loading assets at runtime and to aid in efficient transfer to the GPU for certain data types.
The order of the scenes in the Scene List in your project determines the way that Unity packs together shared assets as follows:
level file, unless it’s an object that’s stripped out (for example an Editor-only component).sharedasset file then it’s assigned to the sharedasset file corresponding to the scene currently being processed. For example, level2 populates sharedassets2, but it can also reference objects in sharedassets0, sharedassets1, globalgamemanagers.assets, resources.assets, and unity_default_resources.This algorithm ensures that objects are only built once, rather than duplicating the assets across multiple scenes. It prioritizes efficiency of the first scenes in the scene list at the expense of later scenes. For example, level0 has the least references of other files and can only reference sharedassets0, globalgamemanagers.assets, and unity_default_resources. In contrast, level99 might reference objects spread over 100 sharedasset files, globalgamemanagers.assets, resources.assets, and unity_default_resource.
The algorithm gives specific preference to the first scene, because it’s the first to load when the application starts.
You can optionally compress Player data into an LZ4 ArchiveFile, by specifying BuildOptions.CompressWithLz4. This is the same file format that Unity uses to archive AssetBundles.
The compressed file for Player builds is always called data.unity3d and contains the global game managers (globalgamemanagers) serialized files, scene serialized files (level and sharedassets files), Resources serialized files (resources.assets), and shader serialized files (Resources/unity_builtin_extra).
It doesn’t contain Resources/unity default resources, because the content build doesn’t generate that file.
It also doesn’t contain any .resource files that contain video and audio content, which are left outside the data.unity3d file.
If you use AssetBundles to build content, then the way Unity assigns objects to files, and the file naming conventions, are different. For more information, refer to AssetBundle build output.