Browser memory is the temporary working space a web browser uses while it runs JavaScript, renders page content, stores variables, and builds objects needed to display a site. It is not a permanent file store; data in memory usually exists only while the page or tab is active. For defenders, that matters because malicious code can create or reconstruct payloads inside the browser without first writing a full malware file to disk.
In attacks, browser memory is often abused when a fake page or ad runs script that assembles encrypted data, decodes hidden content, or prepares a second-stage payload for download or execution. This can reduce visibility for file-based scanning and make the page itself part of the delivery chain. In defense, browser telemetry, script controls, content filtering, and monitoring for suspicious in-memory behavior help detect this kind of abuse. Browser memory is also important in legitimate security testing, where analysts inspect how code behaves before it becomes a file or network event.