Guide to AdMob Mediation (bidding & waterfall)

What is mediation? 

Mediation lets you manage the ad sources used to serve ads in your apps, all in one place. Using mediation, you can send incoming ad requests to multiple ad sources and help ensure you find the best available ad sources to fill the requests. 

In AdMob Mediation, there are two types of mediation: bidding and waterfall. With bidding, ad sources compete in a real-time auction to fill your ad requests. Waterfall mediation calls ad sources one-by-one based on the average eCPM you set, not what the ad source is willing to pay. 

In AdMob, you can create a hybrid setup by using both bidding and waterfall ad sources in your mediation groups. 

What are mediation groups?

AdMob uses mediation groups to segment your ad traffic based on format, platform, app, ad unit, and country. Mediation groups are combinations of targeting settings that help to optimize the revenue generated by your ad units. You can create mediation groups ahead of time, then add ad units and ad sources as you go, or create them all at once. Instead of setting mediation options for each ad unit repeatedly, you can just set them once for your mediation groups, then add your ad units to the groups you want. 

Get started with mediation

Here are the steps we recommend to get started with mediation. 

Step 1: Create an ad unit

After you’ve set up your app in AdMob, you can create your first ad unit. Ad units are containers you place in your apps to show ads to users. Ad units send ad requests to AdMob, then display the ads they receive to fill the request. When you create an ad unit, you assign it an ad format. Ad formats describe the way ads will appear in your app and where they'll be located.

Step 2: Set up your ad sources 

Next, you’ll want to start setting up your ad sources. You can set up bidding sources and waterfall sources. Just remember that the type of source you set up determines how they bid for your impressions. Bidding sources place bids in real-time and compete in a single auction, while waterfall sources are called individually in the order of their eCPM, which is set by you. 

Step 3: Map your ad units 

Mapping your ad units is an essential step in mediation. This allows AdMob to accurately communicate with your third-party ad source to fill your ad request. Add the required mapping details in the ad source page in AdMob. The required mapping details can vary by ad source and are available in your account with the third-party ad source.

Step 4: Create a mediation group

After you’ve created your ad units and set up your ad sources, you’re ready to create a mediation group. You’ll need to create a mediation group for each of your ad formats. You’ll also need different mediation groups for the platform (Android or iOS). 

Step 5: Set up mediation in your apps

Now that you know which ad sources you want to serve ads from and you've set them up in AdMob, use the Google Developer guide (Android, iOS, Unity) to download and implement the SDKs and adapters in your app.