---
title: "What is Time to Interactive (TTI)?"
description: "Learn what Time to Interactive measured, why it was deprecated in Lighthouse 10, and what metrics replaced it."
canonical_url: "https://unlighthouse.dev/glossary/tti"
last_updated: "2026-07-05T10:27:18.281Z"
---

<warning>

Time to Interactive (TTI) was **removed from Lighthouse 10** in February 2023. Use [TBT](/glossary/tbt) for lab measurement and [INP](/glossary/inp) for field measurement of interactivity.

</warning>

Time to Interactive measured when a page became fully interactive. It was a Lighthouse metric from 2017-2023 before being deprecated due to measurement issues.

## What TTI Measured

TTI marked the point when:

- The page displayed useful content ([FCP](/glossary/fcp) fired)
- Event handlers registered for visible elements
- The page responded to interactions within 50ms

The metric identified a 5-second "quiet window" where no Long Tasks occurred and fewer than 2 network requests were in flight.

## Why TTI Was Deprecated

[Google removed TTI in Lighthouse 10](https://developer.chrome.com/blog/lighthouse-10-0) because:

**Overly sensitive to outliers** - A single late network request or Long Task could dramatically inflate TTI, even if the page felt interactive.

**Better alternatives exist** - [LCP](/glossary/lcp) and Speed Index better indicate when content feels loaded. [TBT](/glossary/tbt) measures main-thread availability more robustly.

**Poor correlation with real experience** - A page could have terrible TTI but still feel responsive to users, or vice versa.

**Field measurement issues** - TTI required long observation periods and was impractical to measure in real user monitoring.

## What Replaced TTI

### For Lab Testing

**Total Blocking Time (TBT)** - Measures cumulative main thread blocking during load. More robust, less sensitive to outliers.

When TTI was removed, its 10% score weight shifted to [CLS](/glossary/cls), making the new Lighthouse weights:

<table>
<thead>
  <tr>
    <th>
      Metric
    </th>
    
    <th>
      Weight
    </th>
  </tr>
</thead>

<tbody>
  <tr>
    <td>
      TBT
    </td>
    
    <td>
      30%
    </td>
  </tr>
  
  <tr>
    <td>
      LCP
    </td>
    
    <td>
      25%
    </td>
  </tr>
  
  <tr>
    <td>
      CLS
    </td>
    
    <td>
      25%
    </td>
  </tr>
  
  <tr>
    <td>
      FCP
    </td>
    
    <td>
      10%
    </td>
  </tr>
  
  <tr>
    <td>
      Speed Index
    </td>
    
    <td>
      10%
    </td>
  </tr>
</tbody>
</table>

### For Field Measurement

**Interaction to Next Paint (INP)** - Measures actual interaction responsiveness across the entire page lifecycle. Became a Core Web Vital in March 2024.

## TTI Thresholds (Historical)

When TTI was active, thresholds were:

<table>
<thead>
  <tr>
    <th>
      Score
    </th>
    
    <th>
      Rating
    </th>
  </tr>
</thead>

<tbody>
  <tr>
    <td>
      ≤ 3.8s
    </td>
    
    <td>
      Good
    </td>
  </tr>
  
  <tr>
    <td>
      3.8s - 7.3s
    </td>
    
    <td>
      Needs Improvement
    </td>
  </tr>
  
  <tr>
    <td>
      > 7.3s
    </td>
    
    <td>
      Poor
    </td>
  </tr>
</tbody>
</table>

## Still Need TTI?

If you have legacy systems that rely on TTI:

- It's still available in Lighthouse JSON output with `score: 0`
- It's hidden from the HTML report
- Scripted access to the JSON value continues to work

However, you should migrate to TBT or INP for meaningful interactivity measurement.

## Migration Guide

<table>
<thead>
  <tr>
    <th>
      Old Approach
    </th>
    
    <th>
      New Approach
    </th>
  </tr>
</thead>

<tbody>
  <tr>
    <td>
      TTI in Lighthouse
    </td>
    
    <td>
      Use <a href="/glossary/tbt">
        TBT
      </a>
      
       (30% of score)
    </td>
  </tr>
  
  <tr>
    <td>
      TTI in field/RUM
    </td>
    
    <td>
      Use <a href="/glossary/inp">
        INP
      </a>
      
       (Core Web Vital)
    </td>
  </tr>
  
  <tr>
    <td>
      TTI CI assertions
    </td>
    
    <td>
      Switch to TBT thresholds
    </td>
  </tr>
</tbody>
</table>

For most sites, the removal of TTI [improved Lighthouse scores](https://www.searchenginejournal.com/lighthouse-10-tti-removal/479789/) since pages typically score better on CLS than they did on TTI.

## Measuring Interactivity Today

Use [Unlighthouse](/guide/getting-started/unlighthouse-cli) to measure TBT across your site for lab data.

For real-user interactivity:

- Chrome User Experience Report (CrUX) for INP field data
- [PageSpeed Insights](https://pagespeed.web.dev/) shows both lab TBT and field INP
- Web Vitals library for custom RUM