Drop a HAR file, paste HAR JSON, or load the example to analyze browser network activity locally.
Supported: HAR 1.2 exports from Chrome, Firefox, cURL and most network tools.
No findings — the capture looks clean.
Select a request to inspect its details, timing and bodies.
DataFormatter HAR Analyzer is a free, browser-based network debugger that parses a HAR 1.2 capture, surfaces failed and slow requests, repeated errors, CORS and caching issues, and shows per-request timing waterfalls and headers — with no signup, no upload and no cloud.
The DevTools network tab is great while a page is open, but once you export a HAR you are left reading a thousand-line JSON file. This workbench turns that export back into something useful: a clean request list with status, time and size, a waterfall that highlights the phase each request spent its time in, and an findings panel that summarizes problems across the whole capture.
Findings are grouped by severity — critical, error, warning, info and healthy — and every finding is an observation about the capture, not a verdict. Where a heuristic needs a threshold (slow requests default to over 1000 ms), the value is adjustable and stated alongside the finding. This keeps the analysis honest: each conclusion is traceable back to the exact request rows that produced it.
Open the Requests view, sort by slowest, and read the timing panel to see whether the delay is the server wait or your DNS and connect phases.
Drop the exported HAR from a customer session and let the findings panel surface the 401s, 404 groups and duplicate calls without reading raw JSON.
Run Sanitize HAR before attaching a capture to a ticket or sending it to a collaborator, so tokens and cookies do not leave with the file.
Yes, it is completely free with no account or signup. Paste a HAR export or drop a .har file and the analysis runs instantly in the browser.
No. The HAR document never leaves your machine — parsing, analytics and waterfall rendering all run locally in your tab. A HAR file can contain URLs, tokens and cookies, so you can also sanitize a copy before sharing it anywhere else.
Any HAR 1.2 export works, including Chrome's Lighthouse and Network record (Export HAR), Firefox, Safari and cURL's --har / -o option. If your capture is in JSON but not recognized as a HAR document, the tool says so explicitly.
Findings are grouped across the whole capture: repeated failing endpoints, groups of 401/403 or 404 responses, the request that dominates a slow page, duplicate calls, oversized payloads, missing security headers and CORS problems. Every finding is a labeled observation with its evidence row, never a guarantee.
Last reviewed September 2026 · DataFormatter team — this tool processes data locally in your browser.