Content update examples

The following examples illustrate how Addressables handles content during an update build.

Content marked as Prevent Updates

In this example, consider a shipped application built with the following Addressables groups:

Local_Static Remote_Static Remote_NonStatic
AssetA AssetL AssetX
AssetB AssetM AssetY
AssetC AssetN AssetZ

Local_Static and Remote_Static have the Prevent Updates property in their group settings enabled.

Existing players have Local_Static on their devices, and might have both of the remote AssetBundles cached locally.

If you modify one asset from each group (AssetA, AssetL, and AssetX), then run Check for Content Update Restrictions, the results in your local Addressable settings are as follows:

Local_Static Remote_Static Remote_NonStatic content_update_group (non-static)
AssetX AssetA
AssetB AssetM AssetY AssetL
AssetC AssetN AssetZ

Because Local_Static and Remote_Static have the Prevent Updates property enabled, Unity moves the modified assets to a new group. The system builds the previous layout, but discards the build results for any new groups.

The example has the following implications:

  • Any changed local assets remain unused on the user's device forever.
  • If the user already cached a non-static AssetBundle, they need to redownload the AssetBundle, including the unchanged assets (in this instance, for example, AssetY and AssetZ). If the user hasn't cached the AssetBundle, they only need to download the new Remote_NonStatic AssetBundle.
  • If the user has already cached the Remote_Static AssetBundle, they only need to download the updated asset (in this instance, AssetL via content_update_group). This is ideal in this case. If the user hasn't cached the AssetBundle, they must download both the new AssetL via content_update_group and the now-defunct AssetL via the untouched Remote_Static AssetBundle. Regardless of the initial cache state, at some point the user have the defunct AssetL on their device, cached indefinitely despite never being accessed.

As such, you end up with the following from a user's perspective:

  • The Local_Static AssetBundle is already on the user's device, which you can't change. The old version of AssetA is no longer referenced and remains on the user's device as unused data.
  • The Remote_Static AssetBundle is unchanged. If it isn't already cached on the user's device, it downloads when AssetM or AssetN is requested. Like AssetA, this old version of AssetL is no longer referenced.
  • The Remote_NonStatic AssetBundle is outdated and replaced with a new Remote_NonStatic AssetBundle with a different hash file. The modified version of AssetX is updated with the new AssetBundle. You can optionally delete the old Remote_NonStatic AssetBundle from the server, and it isn't downloaded from this point forward. If cached, it remains on the user's device indefinitely unless you remove it. For more information, refer to AssetBundle caching.

Content update dependencies

If you change an asset's dependencies, Unity rebuilds it as part of a content update build.

As an example, consider the Local_Static group from the previous example. The assets in this group have a dependency chain that looks like this:

  • AssetA depends on Dependency1, which depends on Dependency2,
  • AssetB depends on Dependency2,
  • AssetC depends on Dependency3

All three dependencies are a mix of Addressable and non-Addressable assets. If you modify any of the assets in this group, when a dependency is changed the entire dependency tree needs to be rebuilt. Additionally, because Local_Static has the Prevent Updates property enabled, Unity moves any modified assets to a new group.

For example, If only Dependency1 is changed and then you run Check for Content Update Restrictions, the resulting project structure looks like the following:

Local_Static content_update_group
AssetA
AssetB
AssetC

If only Dependency2 is changed:

Local_Static content_update_group
AssetA
AssetB
AssetC

If only Dependency3 is changed:

Local_Static content_update_group
AssetA
AssetB
AssetC

Additional resources