Browser cache behavior describes how a browser stores web resources and decides whether to reuse them or request them again. HTTP headers such as Cache-Control, ETag, and Last-Modified help determine how long content can be reused and when it must be revalidated with a server.
In cyber security, caching matters because a browser may reuse content after it has changed, or handle cached responses differently from a fresh response. In attacks involving transformed files, redirects, or active formats such as SVG, those differences can affect which content the browser displays or executes and how security policies apply. Defenders should test cache and redirect behavior across relevant browsers, set deliberate caching headers for user-controlled or transformed content, and avoid relying on a trusted URL alone as proof that its content is safe.