HAR File Analyzer

Analyze HAR files with a waterfall, slowest requests and domain breakdown.

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HAR file
Drop a .har file here
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Analysis

What is a HAR File Analyzer?

A HAR file (HTTP Archive, an open W3C-tracked spec) is a JSON dump of every network request a browser made for a page — URLs, methods, status codes, headers, response sizes, and rich timing information for DNS, TCP, TLS, send, wait, and receive phases. Chrome, Firefox, Edge, and Safari can all export one straight from DevTools' Network panel. This tool reads that HAR and gives you, in a few seconds, the same performance picture you'd get from WebPageTest or a paid RUM tool — without uploading a single byte.

What it produces

  • Summary cards — total requests, transferred bytes, end-to-end duration, distinct domains, slowest single request, biggest response.
  • Status code breakdown — counts grouped by 2xx / 3xx / 4xx / 5xx so 4xx storms and redirect loops jump out instantly.
  • Domain breakdown — top domains by request count and total bytes, with a first-party flag so you can see how much of the page is third-party weight.
  • MIME-type breakdown — bytes attributable to JavaScript, CSS, images, fonts, JSON APIs.
  • Slowest requests and largest responses tables — the two lists you grep for first when something is slow.
  • Mini waterfall — a horizontal bar per request, scaled to the recording's total duration, so you can see render-blocking long-poles and gaps in the timeline at a glance.

Why it's different

Most online HAR viewers either upload your file (a privacy nightmare for any HAR captured against an authenticated page — HARs contain cookies, Authorization headers, and full request/response bodies if you didn't strip them) or only show a single waterfall view. This tool runs entirely client-side so a HAR captured against your staging environment never leaves the browser, and it surfaces the aggregate views — domain mix, MIME mix, slowest, largest — that lead you to the actual bottleneck rather than just visualising what you can already see in DevTools.

Tips

  • Set the first-party domain to immediately see what fraction of bytes belong to third parties.
  • Open DevTools, hit Disable cache, reload, then right-click the request list and Save all as HAR with content for the most accurate baseline.
  • Sensitive headers? Use tools like har-sanitizer to scrub Authorization and Cookie values before sharing.

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