Google Ads will stop responding to multicall requests within hybrid setups from January 2024.

The announcement comes as the platform continues its gradual transition from waterfall to real-time bidding auctions for publisher apps.

Why we care. Publisher apps must ensure they comply with the updated rules, as Google Ads has issued a warning that it will cease purchases from publishers deliberately evading multicall detection.

Risks of non compliance. Starting January 20, 2024, Google Ads may suspend purchases on publisher apps for one week to one month, depending on the extent of previously detected abuse. The platform is actively investing in systems to identify publishers attempting to bypass multicall detection, emphasizing a focus on detecting multicall behavior.

Evading multicall detection. An example of a technique employed to evade mutlical detection includes but is not limited to: 

• Ad unit representation: This involves frequently creating, using, or changing new ad units in multicall queries. Ad unit misrepresentation is usually done to hide the presence of related multicall requests.

Why now? Starting October 31, 2023, Google Ads stopped buying ads for multicall requests in waterfalls without a bidding ad unit. However, Google continued interacting with waterfall mediation on the condition that there was only a single call within the waterfall, facilitating the transition to real-time bidding. The next step in Google’s strategy is to stop responding to multicall requests within hybrid setups.

What is mediation? Mediation is a tool that helps you efficiently manage the ad sources for displaying ads in your apps. It enables you to send ad requests to multiple sources, ensuring you find the best available options to fill those requests. There are two types of mediation in Google Ads:

• Bidding: With bidding, ad sources compete in a real-time auction to fill your ad requests.
• Waterfall: In waterfall mediation, ad sources are called one by one based on the average eCPM (how much an advertiser pays for an ad space per unit of 1,000 ad impressions) you set, not on what the ad source is willing to pay.

What is a hybrid setup? In AdMob, a hybrid setup uses using both bidding and waterfall ad sources in mediation groups. 

What is an ad source? An ad source is a platform or provider that serves ads in your app. In your AdMob account, go to the ad source page to set up or view available sources. You can find it by logging in, clicking “Mediation” in the sidebar, and selecting either the “Waterfall sources” or “Bidding sources” tab.

Deep dive. Read Google’s announcement in full for more information.