TotalBlocking Time

A lab measure of how long the main thread was blocked during page load, preventing input.

Growth Score · Activation

Definition

What it means

Total Blocking Time adds up the time beyond 50 milliseconds of each long task between first paint and when the page becomes interactive. It is used in lab tests as a stand-in for responsiveness.

Reducing JavaScript lowers it.

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Guides that cover it

Checkout audit: 12 leaksTwelve places a sale leaks, in cost order, with a test and a fix for each one.When to redesign your siteHow to tell a real redesign need from vanity, and how to do it without losing rankings.Fast for real visitorsRead real visits, then fix images, scripts, layout shifts and the slow start.

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FAQ

Quick answers

What is Total Blocking Time?

A lab measure of how long the main thread was blocked during page load, preventing input.

Where does it sit in Growth Score?

It belongs to the Activation pillar, one of the 12 pillars your score is built from.

What should I read next?

Start with Interaction to Next Paint and Long task, then browse the other terms in Activation.

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Nearby in the A to Z

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