Online Tool Store
HAR File Viewer
Open a HAR network capture and read requests by timing, size, and status, with the waterfall and the slow entries surfaced first.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Developer
HAR File Viewer
Frontend preview — no upload or external service.
Capture summary
148 requests, 4.2 MB transferred, 6.1 s to load event. Three requests over 800 ms, all to the same third-party host; two 404s on fonts.
How the HAR File Viewer works
- Export the HAR from a browser's network panel and open it here — the file stays on your device.
- Sort by time to find what is actually slow, rather than reading the waterfall top to bottom.
- Check for repeated requests to the same URL, which usually means a caching header is missing.
FAQ
Does a HAR file contain sensitive data?
Yes — cookies, authorisation headers, and request bodies including anything you submitted. Treat a HAR like a credential dump: never paste one into a service that uploads it, and scrub it before sharing.
What should I look at first?
The slowest few requests and anything returning an error. A waterfall read top to bottom mostly shows you the order things happened, not what caused the delay.
Why do I see the same URL requested repeatedly?
Usually a missing or too-short cache header, or a script fetching in a loop. Repeated identical requests are one of the easiest wins in a slow page.
How we compare
| Feature | Online Tool Store | A CLI script | An IDE plugin |
|---|---|---|---|
| Sorted by slowest first | ✓ | ✓ | ✓ |
| File never uploaded | ✓ | ✓ | ✗ |
| Works without devtools open | ✓ | ✗ | ✓ |
| Live capture | ✗ | ✓ | ✓ |
HAR File Viewer keeps the capture on your device, which matters because a HAR routinely contains session cookies and authorisation headers.