What is a HAR File and How to Inspect It Safely
An HTTP Archive (HAR) file is a standardized JSON-formatted record of a web browser's interaction with a web application. It logs every HTTP request made by a page, including request/response headers, query string parameters, cookies, payloads, and detailed sub-millisecond network timing waterfalls.
The Security Hazard of Sharing HAR Files
When software vendors or SaaS support teams ask you to "attach a .HAR file to reproduce the bug," they often don't warn you that standard browser HAR exports include:
- Session & Authentication Cookies:
connect.sid,session_id, and OAuth tokens that can allow anyone holding the file to hijack active accounts. - Authorization Headers:
Bearer <JWT>andBasic <base64>credentials. - API Secret Keys: Stripe secret keys (
sk_live_...), AWS credentials, and GitHub personal access tokens passed in headers or query strings.
This tool analyzes HAR files 100% locally in your browser (no data is ever sent to a server) and provides an automated "Sanitize & Export Clean HAR" button that scrubs all authorization headers, session cookies, and API keys so you can safely send HAR traces to third parties.
Understanding Network Waterfall Phases
- DNS Lookup: Time spent resolving the domain name to an IP address.
- Initial Connection (TCP): Time required to complete the TCP three-way handshake (SYN, SYN-ACK, ACK).
- SSL/TLS Handshake: Cryptographic negotiation between browser and server to establish HTTPS encryption.
- Time to First Byte (TTFB / Wait): Latency between sending the HTTP request and receiving the first byte of response data from the server. High TTFB indicates server-side database bottlenecks or CPU contention.
- Content Download (Receive): Time spent streaming the full HTTP response body across the wire.