Twitter will begin showing ads to users based on their browsing history, it said on Thursday.
Cookies are small files stored in users' computers that contain information about which sites they have visited or where they are logging in from.
Twitter said 10 companies, including BlueKai, AdRoll and Quantcast, will initially provide the tracking data.
Google, Facebook and Amazon are also companies that rely on the cookie-based ad targeting to serve ads.
Twitter said it would abide by requests to disable the feature by users who check the "Do Not Track" option in their browsers.