webtracking.org · free tool

Tracking → Core Web Vitals Impact

Estimate what the tracking on a page costs its Core Web Vitals — transfer weight, main-thread time, and a qualitative LCP/INP risk band. Check a stack of tags before you ship, or paste a real page’s resources and see which bytes belong to trackers.

100% client-side — runs entirely in your browser, nothing is sent anywhere · works offline

BETA · estimates only — rough, public order-of-magnitude figures and a labelled heuristic, not a Lighthouse run

JavaScript is disabled — the estimator needs it to compute totals and risk bands; the controls below will not respond. Nothing is sent to a server either way.

Tick the trackers a page loads. The totals below sum approximate transfer weight and main-thread time from the catalog, and map the added main-thread work onto an LCP/INP risk band. Every number is a rough estimate.

These are estimates, not measurements. Catalog figures are rough, public order-of-magnitude values that drift over time, and the main-thread cost is derived from a single heuristic (see the note under “From a real page”). Use them to compare the relative weight of tag choices — for a real number, run Lighthouse or WebPageTest on the actual page.

Feed this a real page’s resources three ways: drop a .har export, paste the JSON from performance.getEntriesByType('resource'), or paste a plain list of URLs (one per line). It sums transfer weight, flags known tracker origins, and estimates main-thread time from script bytes.

One-click resource grab (bookmarklet)

Drag this to your bookmarks bar, then click it on any page to copy that page’s resource-timing JSON to your clipboard — paste it below. It runs entirely in your browser.

CWV resource grab

Drop a .har file here — or click to choose one

… or paste resource JSON / a URL list

How the main-thread estimate works. There is no way to measure real CPU time from a static page, so this uses a documented rule of thumb: roughly 1 ms of main-thread parse + compile + execute time per KB of script transferred, on a mid-tier mobile CPU. Styles, images and fonts are counted toward transfer weight but not toward main-thread time. Real cost varies widely with code shape and device — treat the ms figures as an order-of-magnitude estimate, and the tracker tags as a best-effort host match.

Weight is only half the story

This page estimates what tracking costs your users in load time. It can’t tell you what those trackers actually collect or where they ship it — that takes auditing a live site. ad.rip does exactly that.

Audit a site with ad.rip → Privacy guides

Runs entirely in this browser — no account, no server, no analytics. Related: privacy & tracking guides · all free tools