AdMob uses ad unit IDs to identify unique ad units in your apps, serve ads to those ad units, and manage mediation if it's enabled.
Apps you may have monetized in legacy AdMob used legacy Publisher IDs to identify the ad units and legacy Mediation IDs for mediation. Both of these IDs have been replaced by a single new ad unit ID. To benefit from all of AdMob's mediation features, you need to update the legacy IDs in each of the ad units in your apps to their corresponding new ad unit IDs, then republish your apps.
Update your legacy IDs
To update your the legacy Publisher and Mediation IDs in your apps to the new ad unit IDs:
- Sign in to your AdMob account at https://apps.admob.com.
- Click Apps in the sidebar.
- Click the name of the app you want to update.
- Scroll down to view the ad units table. It displays all of the ad units associated with the app.
- Click the
icon in the Ad unit ID column beside the ad unit.
- In your app's code, replace the legacy Publisher ID and the legacy Mediation ID for the ad unit with its new ad unit ID. Repeat this step for each pair of legacy Publisher and Mediation IDs.
- Publish your app containing the new ad unit IDs.
You may want to wait to publish until your next scheduled app release if you're still actively developing the app. However, to benefit from all of AdMob's mediation features, you need to update and republish the app using the new ad unit IDs.
The new ad unit IDs will be used for ad serving to all of the users who download the new version of your app or update their existing version.