Glossary · Performance

TTI (Time to Interactive)

Time to Interactive was a Lighthouse metric marking when a page looked loaded and reliably responded to input; it was removed from scoring in Lighthouse 10.

Updated October 6, 2026

TTI (Time to Interactive) estimated the moment a page had rendered useful content, registered event handlers and could respond to user input within 50 ms. Lighthouse found it by looking for a quiet window of five seconds after FCP with no long tasks and few network requests.

Why it matters

TTI described the gap between a page looking ready and being usable, a common failure of JavaScript-heavy sites. It was dropped from the Lighthouse performance score in version 10 (2023) because it was sensitive to outliers and a single late request could move it dramatically. Total Blocking Time and INP now cover that ground more reliably.

Example

FCP at 1.2s   page visible
Long tasks until 4.0s while a framework hydrates
5 s quiet window begins at 4.0s

TTI is the end of the last long task: 4.0s

Common misconceptions

  • A page that looks complete is interactive. Hydration or large scripts can leave buttons dead for seconds.
  • TTI is still a ranking factor. It was never part of Core Web Vitals.
  • It can be measured from real users. It is lab-only.

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