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HomeGlossaryHTTP Archive (HAR)
Network

HTTP Archive (HAR)

A file that saves all the network requests your browser made, used by developers to fix slow websites.

Detailed Explanation

An HTTP Archive (HAR) file is a standardized format (RFC specification draft) used by web browsers and network debugging tools to record HTTP tracking information. A HAR file captures detailed information about every HTTP transaction, including URL requests, response status codes, custom headers, cookies, redirects, payload byte sizes, and granular timing breakdowns (DNS, SSL, TTFB, download). You can test this using the HAR Viewer.

Key Technical Takeaways

  • Exportable directly from browser DevTools (Network tab -> Export HAR).
  • Contains complete waterfall timing diagnostics to identify slow resources.
  • Essential for troubleshooting Core Web Vitals, API latency, and CDN caching behaviors.
  • May contain sensitive session cookies or tokens; inspect using client-side viewers.
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