# bundleDefinitions

> Array defining the name and contents of each AssetBundle. (optional)

## Definition

* **Type:** Property
* **Namespace:** [UnityEditor](/engine/6000.5/script-reference/unityeditor.md)
* **Assembly:** UnityEditor.CoreModule

```csharp
public AssetBundleBuild[] bundleDefinitions { readonly get; set; }
```

### Remarks

An array of [AssetBundleBuild](/engine/6000.5/script-reference/unityeditor/assetbundlebuild.md) structs that define the names and contents of each AssetBundle, e.g. the "Build Map". When provided Unity builds only the AssetBundles as specified, and ignores any AssetBundle assignments that had been made in the Editor user interface. This approach makes it convenient to programmatically define AssetBundle contents or to perform builds with different content within the same project.

This field can be left unassigned, e.g. null, in which case [BuildPipeline.BuildAssetBundles](/engine/6000.5/script-reference/unityeditor/buildpipeline/buildassetbundles.md) uses the AssetBundle assignments made in the Editor to determine the AssetBundles and their contents.  Those assignments are stored in the AssetDatabase and in the .meta files and can also be accessed programmatically, see [\_assetBundleName](/engine/6000.5/script-reference/unityeditor/assetimporter/assetbundlename.md), [AssetDatabase.GetAssetPathsFromAssetBundle](/engine/6000.5/script-reference/unityeditor/assetdatabase/getassetpathsfromassetbundle.md) and [AssetDatabase.GetImplicitAssetBundleName](/engine/6000.5/script-reference/unityeditor/assetdatabase/getimplicitassetbundlename.md).