Page override is a browser feature that lets an extension replace a built-in page, such as the New Tab page, with a custom page of its own. The replacement is usually defined by the extension and loaded instead of the browser’s default interface, which gives the extension control over what the user sees first.
This matters because built-in pages sit on a trust boundary: they shape navigation, search, and other core browser behavior. In legitimate use, page overrides can provide enterprise dashboards, internal search pages, or productivity tools. In abuse, the same feature can be used to redirect users, change search habits, or present a lookalike page that pushes unwanted links or phishing content. Defenders reduce this risk by limiting which extensions may override sensitive pages, reviewing extension permissions, and preferring managed policy settings over uncontrolled customization.