A HAR file, or HTTP Archive, is a browser-generated network log that records page requests and responses in a structured format. It typically includes URLs, headers, cookies, status codes, timing data, and other details about how a web session behaved.
In cyber security, HAR files are useful for troubleshooting authentication problems, API failures, redirect loops, and proxy issues. They are also sensitive: a shared HAR can expose session tokens, CSRF values, internal endpoints, user identifiers, and sometimes request bodies or uploaded data. Attackers may ask victims to export and send a HAR file during “support” conversations, then mine it for secrets or account access. Defenders use HAR analysis to trace request chains, confirm whether data was sent to third-party services, and spot unexpected logging or leakage paths. Treat HAR files like credentials and redact them before sharing.