Content Blocker
Apple's name for the sandboxed extension API on iOS Safari that returns blocking rules.
On iOS and macOS Safari, Apple doesn't allow extensions to read or modify web requests directly. Instead, content blockers return a JSON ruleset, and Safari applies it natively. This is the same architectural idea Chrome later adopted with Manifest V3's declarativeNetRequest.
From a user's perspective, a Safari content blocker is just an app that adds ad-blocking rules; you enable it once in Safari settings and it works system-wide.
Related terms
A browser extension or app that prevents advertisements from being downloaded or displayed.
The current Chrome extension platform, which replaces the webRequest blocking API with declarativeNetRequest.
The Manifest V3 API that lets extensions block or modify network requests using pre-declared rules.