Until recently, advertisers have been able to track users across their iPhones and the web using the Identifier for Advertisers (IDFA), a unique identifier that could be accessed by the apps you used and the site you visited. From version 14.5 of iOS, Apple gives you the option to opt out of tracking that apps would normally try to do. This guide shows you where to find these settings on your phone, and how to tweak them to keep pesky data hungry companies off the radar.