The change announced on Friday will end a practice that Google has embraced since the company introduced Gmail in 2004, even though it raised concerns among privacy watchdogs and creeped out some users.
To help finance the free service, Google has been scanning through what Gmail users were discussing and then showing ads connected to some of the topics. Someone writing about running, for instance, might see ads for Nike or Asics shoes.
Google still plans to show ads within Gmail. But instead of scanning through email content, the company's algorithms will rely on other signals to determine which ads are most likely to appeal to each of its 1.2 billion Gmail users.