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[ REAL USER MONITORING // DOCUMENTATION ]

Field data,
not lab guesses

One script tag records Core Web Vitals, long tasks and errors from real sessions, then ships them as small beacons to your endpoint. No package, no build step, no framework.

Start collecting → Read the payload
index.html
<script src="https://insightjs.com/l.js"></script>
01 / INSTALL

One tag

Add the script and it starts collecting. Call init only when you need options.
02 / ROUTES

Views that follow the router

pushState, replaceState and popstate each become one page view, debounced and deduped.
03 / VITALS

Field numbers

LCP, CLS and INP with a FID fallback, plus TTFB, DOMContentLoaded and load.
04 / PAYLOAD

A fixed envelope

Thirteen fields, one {payload}; custom events stay inside the opaque record.

Start here

  • Getting started - add the tag and watch the first beacon leave the page.
  • Configuration - endpoint, disabled and debug options, plus the small public API.
  • Events and payload - the {payload} envelope, page views, custom events, and the session record.
  • Web vitals - LCP, CLS, INP/FID and navigation timing.
  • Errors - error and rejection counts.
  • Changelog - what changed, and what has not shipped yet.
  • Privacy - what is collected and what deliberately is not.
  • Contact - where to report a problem.