Privacy Badger is a web browser extension for Mozilla Firefox and Google Chrome by the Electronic Frontier Foundation (EFF) that detects and blocks advertisements that track user’s browsing. Those that are caught by the extension can get their services unblocked by proving to the EFF that they are willing to respect Do Not Track requests.
If a third-party server appears to be tracking you without permission, by using uniquely identifying cookies to collect a record of the pages you visit across multiple sites, Privacy Badger will automatically disallow content from that third-party tracker. In some cases a third-party domain provides some important aspect of a page’s functionality, such as embedded maps, images, or fonts. In those cases, Privacy Badger will allow connections to the third party but will screen out its tracking cookies.
images via Electronic Frontier Foundation