Focus & Visibility Guard од mwelford

Focus & Visibility Guard prevents websites from detecting when you switch tabs, minimize windows, or switch to other applications. It intercepts the Page Visibility API (document.visibilityState, document.hidden) and window focus/blur events, keeping your browser state private from website scripts.

Common use cases include online exams, timed assessments, or any situation where you want to prevent a site from reacting to tab switches. The extension works entirely in the browser — it collects no data, makes no network requests, and stores all settings locally using browser.storage.local.

Source code: https://github.com/mwelford2/focus-visibility-guard