Reduce Total Blocking Time (TBT)
Break up long JavaScript tasks so the page stays responsive to taps and clicks.
What it means
TBT measures how long the page's main thread is blocked by long JavaScript tasks after a visitor can first see the page. A blocked page looks loaded but ignores taps, scrolls, and clicks.
Why it matters
Visitors perceive an unresponsive page as broken and leave. Google's field data (INP) uses the same signal, so high TBT drags both rankings and conversions down together.
How to fix it
- Run PageSpeed Insights and note which third-party scripts dominate (chat widgets, analytics, ads, embeds are the usual suspects).
- Remove every third-party script you don't actively use — each one runs on the same main thread as your page.
- Defer the rest: load non-essential scripts after the first user interaction or with the async attribute.
- If you use a JavaScript framework, enable code splitting so each page only downloads the code it needs.
- Break up long tasks in your own code with setTimeout scheduling or a web worker for heavy computation.
Helpful tools
- PageSpeed Insights
- Chrome DevTools → Performance
- Lighthouse
Not sure if this affects your site? Analyze your website for free or compare it with a competitor.
Related guides
- Fix slow Largest Contentful Paint (LCP): Make the biggest visible element on your page load in under 2.5 seconds.
- Stop layout shifting (CLS): Reserve space for images and embeds so the page stops jumping while loading.
- Improve mobile page performance: Cut image weight, JavaScript, and server lag so the page loads fast on phones.
- Convert images to WebP or AVIF: Modern image formats are 25–50% smaller than JPEG/PNG at the same visual quality.