All tools

HAR Viewer

Inspect browser network recordings (HAR)

Open a HAR file to see every request with timing waterfall, sizes, status codes and headers, and find the slowest calls, all locally.

How to use HAR Viewer

  1. Export a HAR from your browser’s DevTools Network tab (“Save all as HAR”), then drop it on the page or use Open file. Try an example loads a sample.
  2. Use the filter box to narrow requests by URL, method, status or type, and click a column heading to sort (click again to reverse, a third time to clear).
  3. Read the Waterfall column: each bar starts when the request started and is split into blocked, DNS, connect, SSL, send, wait and receive time.
  4. Click a URL to see its headers, query string, post data and a text preview of the response. The Summary lists totals, the slowest 10 requests and counts by domain and type.

How it works

The file is parsed as JSON in a background worker, and the worker keeps the full entries so only a small row per request reaches the page. Size uses the transfer size when the HAR has one, otherwise the body size, otherwise the content size. Request start times are measured from the first request. HAR’s connect time includes SSL, so SSL is shown separately and subtracted from connect. Only the rows on screen are drawn, so large recordings stay responsive.

Response bodies are shown as text only: text, JSON, XML, JavaScript and similar types are decoded (base64 too) and shown as plain text; images and other binary content are not rendered.

Limits

  • Files up to 200 MB can be opened.
  • The response preview shows at most the first 100,000 characters of a body, and only when the HAR saved the body at all.
  • Only the first sort key can be active, and the filter is a plain text match, not a query language.
  • Pages and WebSocket messages in the HAR are not shown; only the request entries are.
  • Entries that have no timing data are drawn as one “wait” bar covering their total time.

Privacy

HAR files can contain cookies, authorization headers, tokens, form data and response bodies. The file is read and parsed in your browser, in a worker, and is never uploaded or stored; nothing is sent anywhere. Be careful sharing a HAR file itself, and note that this tool has no share link for that reason.

Frequently asked questions

Why is a request shown as “failed”?

The HAR recorded status 0, which browsers use when the request was blocked, aborted or never got a response.

Why is a response preview empty?

Many browsers leave out bodies when exporting a HAR, and binary bodies such as images are never shown. The note under the preview says which case applies.

Is it safe to open a HAR with secrets in it?

Yes for viewing: nothing leaves your browser. The risk is in sharing the file, because cookies and tokens inside it can be used to sign in as you.

More tools