Getting started

What's a HAR file?#

A HAR (HTTP Archive) is a JSON recording of every network request a page made while it loaded: URLs, timings, sizes, headers, and response metadata. Every major browser can export one from its developer tools. It's the raw material Harpoon analyzes — a complete, replayable picture of how your page actually loaded for you.

Exporting a capture from your browser#

Chrome / Edge

1. Open DevTools (F12 or Cmd/Ctrl+Shift+I) → Network tab.
2. Tick Preserve log, then hard-reload the page (Cmd/Ctrl+Shift+R) so the capture starts from a cold load.
3. Click the export arrow (↓) above the request table — choose the sanitized HAR export if offered (it strips cookies).

Firefox

1. Open DevTools → Network tab and reload the page.
2. Click the gear icon on the right of the toolbar → Save All As HAR.

Safari

1. Enable the Develop menu (Settings → Advanced → Show features for web developers).
2. Develop → Show Web Inspector → Network tab, reload, then click Export.

• Capture in a private/incognito window so browser extensions don't pollute the recording.
• Let the page finish loading (spinner stops, network goes quiet) before exporting.
• For a before/after experiment, capture both states the same way — see Comparing runs.

Analyzing it#

The Analyze page takes input two ways. Paste a page URL and Harpoon loads it in a headless browser, records the HAR for you, and analyzes it in one step — no DevTools detour. Or drop a .har file you recorded yourself. Both paths work without an account and return the same full analysis.

Either way the same deterministic engine parses every request, builds the waterfall, runs its rule set (caching, compression, render-blocking, third parties, redirects, and more), and scores the page 0–100. The same file always produces the same findings — there's no sampling and no model in that loop.

The result includes the deterministic findings and the AI explanation, whether or not you sign in. Create an account to keep reports in your workspace; paid plans add scheduled monitoring and longer-term trends.

Upload limits#

• Uploads up to 100 MB, signed in or not. Anonymous analyses are rate-limited per IP.
• Captures with an extreme number of requests are refused (50,000+ entries) — that's virtually always a runaway recording, not a page load.

Hitting a size limit usually means the recording ran too long — re-capture just the page load rather than a whole browsing session.

Next steps#

• Reading a report — what the score and findings mean.
• Capturing pages — let Harpoon record the HAR for you, including behind a login.
• Comparing runs — diff a before/after pair.