HAR file analyzer

Drop a .har export from Chrome, Edge, Firefox or Safari and get the same waterfall, per-host totals and render-blocking list — parsed right here in your browser, never uploaded.

No HAR handy?

What a HAR file is

HAR (HTTP Archive) is a JSON log of every request a browser made while a page loaded: URL, headers, status, size and a timings object with blocked, dns, connect, ssl, send, wait and receive in milliseconds. It was specified by the W3C Web Performance working group and every major browser's DevTools can export it.

Because it's recorded by a real browser, a HAR captures what a server-side page speed test can't: requests fired by JavaScript, HTTP/2 multiplexing, your cache state and your actual network. That makes it the best evidence to attach to a performance bug report.

Reading the numbers

  • Queued / blocked (hatched) — the request waited for a free connection or for the browser's scheduler. Lots of it on HTTP/1.1 means too many requests per host.
  • Connect in a HAR includes TLS; we split it so the purple TLS segment shows on its own. How the handshake works.
  • Wait is server time plus one round trip — the per-request TTFB.
  • DOMContentLoaded and Load come from the page's pageTimings and are drawn as dashed lines.

New to waterfalls? The waterfall reading guide has an annotated example you can step through.

Questions developers ask

Is my HAR file uploaded anywhere?

No. The file is read and parsed by JavaScript in your browser tab; it never leaves your device. Only if you press "Explain my results" is a short text summary (URLs, timings and sizes — no cookies, headers or bodies) sent to the AI analyst.

How do I export a HAR file from Chrome or Edge?

Open DevTools (F12), go to the Network tab, tick "Preserve log" and "Disable cache" if you want a cold load, reload the page, then click the download arrow ("Export HAR") in the Network toolbar. In older versions right-click any request and choose "Save all as HAR with content".

How do I export a HAR file from Firefox or Safari?

Firefox: open DevTools, Network tab, reload, then click the gear icon and choose "Save All As HAR". Safari: enable the Develop menu, open Web Inspector, Network tab, reload and click "Export". Both produce a standard HAR 1.2 file this analyzer can read.

Does a HAR file contain sensitive data?

Often, yes: cookies, authorization headers and form posts can be recorded. That is why this analyzer works entirely locally. Before sending a HAR to anyone else, strip cookies and tokens — recent Chrome versions export a sanitized HAR by default.

Why do some requests show no DNS or connect time?

They reused an existing connection. With HTTP/2 and HTTP/3, one connection per origin carries many requests, so only the first request to a host pays DNS, TCP and TLS. A value of -1 in the HAR means "not applicable" and is shown as zero.

Which HAR fields does the analyzer use?

startedDateTime, time and the timings object (blocked, dns, connect, ssl, send, wait, receive) for the bars; response status, content mimeType, _transferSize or bodySize for sizes; pageref and pageTimings for page markers; and Chrome's _resourceType, _priority and _renderBlocking fields when present.