Browser compatibility is the degree to which a website or web app works correctly across different browsers, versions, and operating systems. It covers rendering, JavaScript behavior, media playback, hardware acceleration, input handling, and security-related features such as cookies, storage, and certificate checks.
In cyber security, compatibility matters because the same site can behave differently in Chrome, Firefox, Edge, or Safari, or on Windows versus Linux. Those differences can create false assumptions during testing, break authentication flows, weaken security controls, or expose logic bugs that only appear in one client stack. Attackers sometimes abuse browser-specific quirks, parser differences, or legacy features to bypass filters or trigger unexpected behavior. Defenders use compatibility testing to verify that login pages, dashboards, and streaming clients remain stable, that security headers are honored, and that GPU or codec settings do not degrade secure operation. Good compatibility reduces user friction, but it also narrows the gap between intended behavior and what actually runs in the browser.