The loss of the cookie and other ways to identify people online has caused ad revenue to crater.
"Too soon to say, but the platforms don't like it," said David Temkin, a Google executive who focuses on ads privacy.
"Clean rooms we think are promising because they can respect user privacy," Temkin said.
He notes that clean rooms can be slow and expensive.
The prevalence of retail media already jumpstarted the need for clean rooms in 2022, said Scott Howe, CEO of LiveRamp, which provides clean rooms and identifiers.