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Total Blocking Time (TBT)

Total Blocking Time measures the amount of time between First Contentful Paint and Time to Interactive when the main thread is blocked for long enough to prevent input responsiveness.

Why Total Blocking Time (TBT) Matters

TBT correlates strongly with INP and indicates how responsive a page feels to users. High TBT scores suggest JavaScript execution issues that can harm user experience and Core Web Vitals performance.

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