SAN FRANCISCO — If you have ever wondered why Facebook showed you that advertisement for a new iPhone game or a cheap flight to Bermuda, you will soon be able to find out.
Facebook announced Thursday that it is going to give its users the ability to see the dossiers of likes and interests it keeps on them, as well as the ability to change, add or delete information in those files. And if you don't like an ad, you will be able to tell the social network what types of marketing messages you would rather see.
But even as Facebook gives users more control, it is foraging deeper into their activity on other sites. Facebook's dossiers are based mostly on people's activities on Facebook, such as liking brand pages or sharing a funny ad. Starting next week, the company will also tap data it already collects from people's smartphones and other websites they visit to hone ad targeting.
Users can opt out of such extended tracking, but they will have to visit a special ad industry website and adjust their smartphone settings to do so.
"At the end of the day, it's all about data," said Debra Aho Williamson, who studies social media for the research firm eMarketer. "Marketers want more data to be able to target people. And Facebook wants more data to make the advertising as relevant as possible."
For Facebook, giving users more control while digging further into their Internet behavior could be smart business.
"The thing that we have heard from people is that they want more targeted advertising," said Brian Boland, Facebook's vice president in charge of ads product marketing. "The goal is to make it clear to people why they saw the ad."
It is unclear how privacy advocates and public officials will react to Facebook's efforts to provide more clarity about how its ads work.
Although Facebook will now give its users a way to modify what ads they see, users can't completely get rid of ads.