Free Tool

Third-Party Script Auditor

Enter any URL to see every third-party script, how large it is, how much it blocks the main thread, and what to do about it.

Audit Any URL

Understanding Script Impact on INP

ColumnWhat It MeansGood Threshold
SizeTransfer size over the network (compressed). Bigger = longer parse time.Under 50KB per script
BlockingTime the script blocks the main thread from handling interactions.Under 50ms total
Main ThreadTotal CPU time used. High = slower INP on mobile.Under 150ms total
The dirty secret: Google Tag Manager adds 50–150ms to mobile INP. Chat widgets (Intercom, Drift) can add 200–400ms. 5+ third-party scripts almost guarantees an INP problem on real phones.

Fix by Script Type

Analytics (GA, GTM)

Load with defer. Consider switching to Plausible or Fathom — 1KB vs 45KB, zero INP impact.

Chat Widgets

Delay load by 3–5s after page load. Better: show a fake button, load real widget only on click (facade pattern).

Ad Scripts

Place in <body> footer. Reserve slot dimensions with min-height CSS to prevent CLS.

Social Embeds

Twitter/Instagram embeds load 200KB+. Use lite-youtube-embed for YouTube. Use screenshot + link for tweets.

Advanced: Audit This Page’s Scripts in Browser

Drag to bookmarks bar, then click on any page for an instant pop-up report:

Script Auditor drag to bookmarks bar

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