Time to Interactive (TTI) measures when a page becomes reliably interactive. A page is considered interactive when it displays useful content, event handlers are registered, and the page responds to interactions within 50ms.
TTI thresholds
- Good: 3.8 seconds or less
- Needs Improvement: Between 3.8 and 7.3 seconds
- Poor: More than 7.3 seconds
How TTI is measured
TTI looks for a 5-second window where there are no long tasks (tasks over 50ms) and no more than two in-flight network requests. The TTI is the end of the last long task before this quiet window.
Improving TTI
- Minimize main-thread work
- Reduce JavaScript execution time
- Use code splitting to reduce initial bundle size
- Preload critical resources
- Remove unused JavaScript
Related Terms
First Contentful Paint (FCP)
A performance metric that measures the time from when the page starts loading to when any part of the page's content is rendered on screen.
Interaction to Next Paint (INP)
A Core Web Vital that assesses page responsiveness by measuring the latency of all user interactions throughout the page lifecycle.
JavaScript Execution Time
The time the browser spends parsing, compiling, and executing JavaScript code, which can block the main thread and delay interactivity.
Total Blocking Time (TBT)
A lab metric that measures the total amount of time the main thread was blocked long enough to prevent input responsiveness.