HAR File Inspector (HTTP Archive Viewer)
File
When you record network activity in browser DevTools and export the result, you get a HAR (HTTP Archive) file — a JSON document containing every request, response, and timing from the recording. Loading it back into the browser is awkward (you need DevTools open, and big HARs slow it down). This inspector parses the HAR locally and surfaces the things you usually want: how many requests, total transfer size, total wall time, how many unique hosts. Then it breaks down the requests by content type (document/script/stylesheet/image/font/xhr/media) with per-type byte totals, and by status band (2xx/3xx/4xx/5xx) so failures jump out. Top-5 slowest and top-5 largest tables surface the obvious performance suspects. Below the summary, every entry is in a sortable, filterable table — search the URL, narrow by type, isolate errors, sort by size or duration. Nothing is uploaded; the file is parsed by the browser and stays on your machine.
How to use
- In any modern browser open DevTools → Network tab. Reload the page you want to profile. Right-click any request and choose Save as HAR with content (Chrome) / Save All As HAR (Firefox) / Export HAR (Safari).
- Drop the .har file onto this tool — or click and select it from disk.
- Read the summary tiles for the headline numbers (entry count, total bytes, total time, host count).
- Use the by-type and by-status panels to see where weight and errors are concentrated. The slowest/largest tables identify obvious culprits.
- Filter the entries table by URL substring, content type, or success/error to drill in. Sort by size or time to find the heaviest items.
Frequently asked questions
- What's a HAR file?
- HTTP Archive format — a JSON spec maintained by the W3C Web Performance group. Every major browser's DevTools can export the Network panel as a .har file. It contains the timing breakdown for each request (DNS, connect, SSL, wait, receive), full request/response headers, and (optionally) response bodies. This tool reads the standard 1.2 schema.
- Are response bodies shown?
- Not in this view — only metadata (URL, status, size, time, content-type). HAR files can include the actual response payload when you tick 'Include sources' or 'with content' on export. Browsing those bodies is what DevTools is for; this tool focuses on the request-level shape that's easy to summarise.
- How is size measured?
- It uses `response.content.size` (the decoded body byte length) when present and positive; otherwise it falls back to `response.bodySize` (the on-the-wire byte length). For requests with redirects or cached responses, both fields can be 0 or -1; those entries report '0 B' here. Total bytes is the sum of the per-entry numbers — close to but not identical to network transfer because of compression and chunking.
- Why are some entries 'failed'?
- DevTools assigns status 0 to requests that never got a response — DNS failure, blocked by CORS, blocked by an extension, aborted by the user, network drop. They show as 'failed' in the status panel and red in the row.
- Will it leak my HAR somewhere?
- No. The file is read with the browser's FileReader API and parsed in JavaScript on this page. No network request is made with its contents. You can verify in your own DevTools Network tab while the file is loaded — no outbound requests will appear.
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