Which devices does Cognito work on?

The web app is the full Cognito experience and works in any modern browser; including a school laptop where you cannot install anything. Sign in and study, that is all.

On top of that, three apps are in the works: an Android app (with home-screen widgets, screen time and app blocking), a Windows app (Focus Mode for your whole PC) and a Chrome extension (website blocking). See When are the apps coming out?