Apple (NASDAQ: AAPL) and Facebook (NASDAQ: FB) generally aren't considered competitors, since the former mainly sells hardware, software, and services and the latter generates nearly all its revenue from ads.
However, the relationship between the two tech giants has grown increasingly hostile in recent years. After repeatedly criticizing Facebook's targeted advertising practices, Apple revealed an upcoming update for iOS 14 that will allow users to opt-out of data tracking across all iOS apps.
Facebook bought full-page newspaper ads to protest Apple's move, and claimed it could reduce ad revenue from its third-party Audience Network by over 50%. Apple still plans to release the update later this year.
Source Fool.com