HAR File Performance Analyzer

What does this tool analyze?

It takes a HAR (HTTP Archive) network capture and turns it into a performance report: overall timing statistics, a breakdown by content type and by domain, and the slowest and largest individual requests — everything you'd otherwise have to eyeball manually in DevTools' Network tab.

How this tool works

1. Paste HAR JSON into the input box, or upload a .har file.
2. Optionally filter to a specific content type or status class before analyzing, and choose how many entries to show in the slowest/largest lists (Top N).

The Summary table reports total requests, transfer and content size, average/median/p90 request time, average time-to-first-byte (TTFB), and a success/redirect/error breakdown. By Content Type and By Domain show where your requests and bytes are actually going. Slowest Requests and Largest Requests surface the individual outliers worth investigating first.

Why median and p90, not just average

A single very slow request can pull the average up without representing the typical experience. The median (p50) shows what most requests actually looked like, while the p90 shows what the slower 10% experienced — together they give a much more honest picture of network performance than an average alone.

What TTFB tells you

Time-to-first-byte (the wait timing in HAR terms) is the gap between sending a request and receiving the first byte of the response — it's dominated by server processing time, not network transfer. A high average TTFB usually points to backend/API slowness rather than a bandwidth problem.

Common uses

• Diagnosing why a page feels slow by finding the actual slowest requests
• Identifying which domain or third-party script is responsible for the most network weight
• Comparing performance across two HAR captures (before/after an optimization)
• Spotting a handful of oversized assets dragging down page load

Privacy

This tool runs entirely in your browser. Your HAR file is never uploaded to a server.