Browser chrome is the browser-controlled interface around a web page, including the address bar, tab strip, navigation buttons, lock icon, and other security indicators. It is separate from the page content and is supposed to be controlled only by the browser itself, not by the site being visited.
This matters because users often trust what browser chrome shows before they enter passwords, approve payments, or accept downloads. Attackers try to spoof or imitate these cues with fake address bars, fullscreen overlays, pop-up windows, or visual tricks that make a malicious site look like a legitimate one. In defense, browser chrome is a key trust boundary: browsers must prevent pages from altering it, and users should verify the registrable domain and security indicators, not just the overall appearance of the page.