---
type: Glossary Term
title: "Time to Interactive (TTI)"
description: "The time until the main thread is reliably free to handle user input."
resource: "https://prerendering.com/glossary/tti"
tags: [metrics, glossary]
timestamp: 2026-05-11T00:00:00Z
---

# Time to Interactive (TTI)

The time until the main thread is reliably free to handle user input.

TTI measures when a page becomes reliably interactive — main thread free, event handlers wired, no long tasks. Replaced by INP in Core Web Vitals but still used in Lighthouse and lab measurement. Long TTI signals heavy hydration cost or third-party JS bloat.

Also known as: TTI.