Inspect a HAR capture
A HAR file is the browser's request log — who was called, how long it took, and how much moved.
Tools used in this guide
The job
DevTools can export a HAR when a page misbehaves. Reading it answers: which requests ran, which were slow, what failed with 4xx/5xx, and how heavy the page's traffic was.
Drop the .har file
The viewer parses HAR 1.2 JSON and lists each entry's method, host, path, status, total milliseconds, transferred bytes, and MIME type. Filter and sort to find the outliers.
Worked example
A support ticket says 'the export button hangs': the HAR shows a /api/export POST taking 30,012 ms then returning 504 — the client side was fine; the server timed out.
Where it stops
Entries show timing and size, not bodies — request/response payloads aren't decoded. HAR files can contain cookies and tokens; this viewer never uploads the file, but share the file itself carefully.