# How to reduce Total Blocking Time (TBT)

> TBT adds up every moment the page is frozen by JavaScript while loading. Under 200 ms keeps the page responsive. It is the lab stand-in for INP.

Speed & Core Web Vitals · HTML version: https://getreport.app/learn/total-blocking-time

## Total Blocking Time

Passing looks like: Total Blocking Time passes.

**Why it matters.** TBT adds up every moment the page was too busy running JavaScript to respond to a tap. It is the lab stand-in for INP and the heaviest-weighted Lighthouse metric.

**How to fix it.**

1. Remove or defer JavaScript that is not needed for the first screen (defer, async, or load on interaction).
2. Split long tasks (> 50 ms) into smaller chunks; move heavy work to a web worker.
3. Audit third-party tags — chat widgets, tag managers and A/B tools are the usual culprits.

Check your own page: https://getreport.app/