When you build a Player in Unity, the UnityLinker process runs to reduce the size of the assemblies by removing unused types. This process can strip the following:
MonoBehaviour and ScriptableObject instances. Unity can strip these from core Unity assemblies like UnityEngine.dll and Unity.dll, but preserves them in custom assemblies once those assemblies are marked as used.The affect that code stripping has on content appears in the Player as null reference exceptions, missing type errors, or crashes. Additionally, AssetBundle or Addressables content-only build can’t use types that have been stripped out of a Player build.
You can use the Build Report Inspector’s Stripping tab to inspect which modules and types have been preserved in a Player build.
You can prevent the linker from stripping code in the following circumstances:
Unity might strip a Unity object type that’s present in AssetBundles, but not in any sceneA Scene contains the environments and menus of your game. Think of each unique Scene file as a unique level. In each Scene, you place your environments, obstacles, and decorations, essentially designing and building your game in pieces. More info
See in Glossary or asset included in a Player build. This means that content from the AssetBundle might work when testing in Play mode, or on builds with minimal code stripping, but errors or crashes occur in a Player built with code stripping enabled.
To resolve this, you can create a custom build script that directly includes the AssetBundle’s manifest file, as follows:
.manifest file for each AssetBundle, and a root .manifest file with the same name as the output folder..manifest file into the Player build process with the BuildPipeline.BuildPlayer API.For more information, refer to AssetBundle file format reference and BuildPlayerOptions.assetBundleManifestPath.
You can also use the Preserve attribute, or manually author a link.xml file in your project, to further influence the code stripping behavior.
If a type of Unity object is present in content built with Addressables, but not in any scene or asset built into the Player, then Unity might strip that type.
Addressables automatically generates a link.xml file inside the Library/com.unity.addressables folder describing types used in the content. The Player build takes this link.xml file into account, provided the Addressables content has been built before, or at the same time as, the Player build.
You can also use the Preserve attribute, or manually author a link.xml file in your project, to further influence the code stripping behavior.
You can’t use a link.xml file to prevent entire Unity modules (for example AI or Physics) from being stripped.
If you need to use types from a module in an Addressables build, make sure the Player build includes some content that references that module. For example, to keep the Physics module, add a component such as a RigidbodyA component that allows a GameObject to be affected by simulated gravity and other forces. More info
See in Glossary or ColliderAn invisible shape that is used to handle physical collisions for an object. A collider doesn’t need to be exactly the same shape as the object’s mesh - a rough approximation is often more efficient and indistinguishable in gameplay. More info
See in Glossary to a GameObjectThe fundamental object in Unity scenes, which can represent characters, props, scenery, cameras, waypoints, and more. A GameObject’s functionality is defined by the Components attached to it. More info
See in Glossary in a scene included in your build. This creates a dependency that the Player build process recognizes, and preserves the module.
Player builds record the used types in a ScriptsOnlyCache.yaml file inside the Library/PlayerDataCache folder, which you can look at to diagnose any code stripping issues. This file is used to support the Incremental build pipeline which can reuse the content from a previous Player build. In that case the Player build passes the cached type usage from that file to the Unity linker.
Note: The ScriptsOnlyCache.yaml file uses an internal format that might change in future Unity versions. To control code stripping, use link.xml files in your project instead of modifying this file directly.