Shut Up is a free comment-blocking tool that uses shutup.css to hide comment sections across websites by default. Available as a browser extension for Chrome, Firefox, Edge, Opera, and Safari, plus an iOS/iPadOS app, it helps users avoid toxic online discussions.

Built on Steven Frank's stylesheet, Shut Up injects CSS rules into nearly all visited pages to hide comments automatically. Users can easily toggle comments on with a single click or tap when needed. The tool works on iPhone 5s and newer, iPad Air and newer, and requires iOS/iPadOS 12 or later.

Privacy-conscious users will appreciate that Shut Up doesn't track browsing activity beyond periodic stylesheet updates. The extension only contacts the server for the latest shutup.css version, with temporary diagnostic logs recorded. For sites where comments add value like GitHub or Stack Overflow, users can configure comments to show by default. The tool addresses the growing problem of online toxicity while maintaining flexibility for constructive discussions.