HAR Viewer

How to use it

1. Pick a .har file exported from Chrome, Firefox, Edge or Safari DevTools, or paste the HAR JSON into the panel.
2. Click Analyze. The file is read with FileReader inside the page, so the recording never leaves your machine.
3. Read the Summary: request count, hosts, wall clock span, sum of times, median, transferred bytes and error count.
4. Use the waterfall to find gaps. Each bar starts at the request offset and ends when the response finished, so long bars and late starts are both visible.
5. Change Sort by to duration or size when you want the outliers grouped instead of ordered by time.

Common use cases

• Finding the slow call - sort by duration and check the Top 5 list before reading hundreds of rows.
• Checking what a page loads - exported HAR files list every request including redirects, preloads and failed assets.
• Confirming cache behavior - 304 responses with a small body size show up as short bars with zero payload.
• Sharing a reproduction - export the HAR from a colleague's browser and inspect it here without installing tooling.
• Sizing a payload problem - sort by size to see which responses dominate the transferred total.

Why it stays private

A HAR recording contains cookies, authorization headers, session URLs and sometimes response bodies. This tool reads the file into memory with FileReader and parses it with JSON.parse. No fetch, no upload, no analytics on the content, so recordings from production sessions are safe to open here.

FAQ

Q: Which HAR fields are read? A: log.entries with request.url, request.method, response.status, response.bodySize, response.headersSize, entry.time and entry.startedDateTime. The optional _transferSize field is used when present, because it is the more accurate number for compressed transfers.

Q: Why is the transferred total incomplete? A: Some exporters write -1 for bodySize or headersSize. Those entries are counted, but excluded from the byte total, and the summary states how many entries reported a size.

Q: Are request and response bodies analyzed? A: No. Only timing, status and size metadata is read. Bodies stay inside the parsed object in memory and are never rendered, so secrets in payloads are not printed on screen.