Expanded testing elements
Google’s latest update responds to a long-standing call from brands and advertisers for greater control, sources told ADWEEK. The tech giant first teased split testing for Pmax about 18 months ago, though the feature has faced repeated delays, according to Goodwin.
Now, advertisers can set a base campaign on Pmax and run an experimental campaign simultaneously, testing elements like creative assets or bidding strategies, sources said. Once the test begins, Google divides traffic equally between the two campaigns, serving either the base or experimental ad to users across search, display, YouTube, and other Google platforms.
After the test period, advertisers can see which campaign performed better.
More nuanced insights
At Tinuiti, nearly 10 clients have requested access to the split testing feature, with many looking to test campaigns that will drive new customer acquisition, according to Merklin. Other elements marketers can test include smart bidding strategies (adjusting bids based on goals like cost-per-acquisition or return on ad spend), final URL expansion, audience signals (inputting custom audiences, like first-party data, to target most relevant audience), and search themes (defining keywords or categories to align with specific search behaviors).
Merklin said that this feature offers a clearer understanding of how changes impact performance while accounting for external variables like seasonality. The result is more reliable insights for the advertiser.
Over reporting performance
Not all buyers are fully on board with the feature, though.
An anonymous executive from a marketing agency said that while Pmax A/B testing has become standard in optimization calls, agency adoption has been slow because buyers still want more control over test elements.
Unlike traditional A/B tests, where two separate campaigns are run against each other, Pmax A/B tests are conducted within the Pmax account—which supports multiple Pmax campaigns across search or display. This lack of separation makes it difficult to isolate the impact of specific changes.
“This is an issue with transparency,” the executive said. “We have seen Pmax cannibalizing search volume from search campaigns running concurrently. We have no insight into whether it is truly valuable or if it’s just an inefficient use of media dollars.”
Rain the Growth Agency, which previously tested split testing for Google Ads outside of Pmax, found that Google’s reports tend to overperform, especially in the B segment of the test.
“Performance has always looked better in those scenarios,” said Stacia Fulginiti, director, paid search + YouTube. “So, we’re wary of fully leveraging these experiments.”