HAR Viewer
Inspect HTTP Archive (HAR) exports from browser DevTools.
Overview
The HAR viewer parses an HTTP Archive file exported from a browser's DevTools and lists every request with its method, URL, status, duration, and size. Slow endpoints, redirects, and failed calls stand out without scrolling through raw JSON.
It's the go-to inspection tool when a colleague or a customer sends a HAR capture for a page that's loading slowly or behaving oddly. Frontend developers, performance engineers, and support teams use a har file viewer to diagnose third-party scripts, redirect chains, and uncached assets without booting up Chrome's DevTools again.
How it works
The HAR specification, maintained by the W3C Web Performance group, defines a JSON document with a top-level log containing entries, each holding request, response, and timings objects. The viewer walks the entries, sorts them chronologically by startedDateTime, and renders a flat table.
Per-request timings are summed from the timings object (blocked, dns, connect, ssl, send, wait, receive) so the total matches what DevTools shows. Response sizes prefer _transferSize when present (real bytes on the wire) and fall back to bodySize for older captures.
Examples
Top requests by duration:
200 GET /api/users 1.2 KB 340 ms
200 POST /api/login 0.4 KB 180 ms
304 GET /static/app.js 0 12 ms
404 GET /favicon.ico 0 8 ms
Filter: status >= 400
404 GET /favicon.ico
500 POST /api/checkout
FAQ
Does it show request and response headers?
Yes — each entry can be expanded to show full request headers, response headers, cookies, and the response body if it was captured. Sensitive headers (Authorization, Cookie) are shown verbatim, so be careful sharing screenshots.
Can I diff two HAR files?
Not directly in this viewer. Use the JSON diff tool on the two HAR exports if you need to compare network captures between sessions.
What about WebSocket frames?
The HAR spec doesn't standardise WebSocket payloads, but Chrome includes them in a non-standard _webSocketMessages field. The viewer surfaces them when present so you can inspect frame direction, opcode, and payload.