In March 2024, Interaction to Next Paint (INP) replaced First Input Delay as Google's responsiveness metric. Here's what you need to know about this Core Web Vital.
What is INP?
INP measures how quickly your site responds to user interactions like clicks, taps, and key presses throughout the entire page visit—not just the first interaction.
INP vs FID
| INP | FID (Old) |
|---|---|
| Measures ALL interactions | Only measured FIRST interaction |
| Captures full responsiveness | Could miss slow interactions |
| More accurate representation | Sometimes misleading |
INP Thresholds
- Good: ≤ 200 milliseconds
- Needs Improvement: 200-500 milliseconds
- Poor: > 500 milliseconds
What Causes Poor INP?
- Heavy JavaScript execution
- Long-running main thread tasks
- Too many third-party scripts
- Inefficient event handlers
- Large DOM size
How to Improve INP
1. Break Up Long Tasks
Split JavaScript into smaller chunks that don't block the main thread for more than 50ms.
2. Reduce Third-Party Scripts
Audit and remove unnecessary scripts. Load non-essential scripts after page load.
3. Optimize Event Handlers
Keep click and input handlers lightweight. Move heavy processing off the main thread.
4. Use Web Workers
Move complex calculations to background threads.
Measuring INP
- PageSpeed Insights (field data)
- Chrome DevTools Performance tab
- Web Vitals Extension
- Google Search Console
Related: Core Web Vitals Explained
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