Google web.dev names three Core Web Vitals. LCP should reach 2.5 seconds or less. INP should reach 200 milliseconds or less. CLS should reach 0.1 or less. Check the 75th percentile of page visits on mobile and desktop. Fixes center on images, fonts, scripts and resource delivery. Set a performance budget so the site remains fast.
Slow pages lose visitors before the first headline appears. Google gives clear targets and a short list of fixes.
Facts follow Google web.dev articles on building fast sites and Core Web Vitals.
Which Metrics Measure Page Speed?
| Metric | What it measures | Good value |
|---|---|---|
| LCP | How fast the main content appears | 2.5 seconds or less |
| INP | How quickly the page responds to input | 200 milliseconds or less |
| CLS | How much content moves unexpectedly | 0.1 or less |
web.dev advises you to judge the 75th percentile of page visits and to check mobile and desktop apart. Lighthouse highlights these metrics.
How do You Increase Page Speed?
- Resource delivery. Improve Time to First Byte, use a CDN, preload critical assets and prioritize resources.
- Images. Choose the right format and compression, serve responsive sizes and replace animated GIFs with video.
- Lazy loading. Apply it to images and video but not everywhere. Too much hurts LCP.
- Fonts. Follow font loading best practices.
- CSS. Reduce the scope and complexity of style calculations.
- Third party scripts. Find slow ones and fetch them efficiently.
- JavaScript. Break up long tasks, split code, remove unused code and minify payloads.
How do You Measure the Result?
web.dev tells you to compare lab data and field data. Lighthouse is a lab tool. Chrome UX Report supplies field data from real users.
Set and enforce performance budgets after launch so the site remains fast.
Related reading: what SEO is and how it works and website security tips.
Frequently Asked Questions
What are Core Web Vitals?
LCP for loading, INP for responsiveness and CLS for visual stability.
What is a Good LCP?
2.5 seconds or less.
What is a Good INP?
200 milliseconds or less.
What is a Good CLS?
0.1 or less.
Does Lazy Loading Always Help?
No. web.dev warns that too much lazy loading can hurt LCP.
Key Takeaways
- LCP, INP and CLS are the Core Web Vitals.
- Judge the 75th percentile on mobile and desktop.
- Images, fonts, scripts and delivery give the biggest fixes.
- Overusing lazy loading hurts LCP.
- Performance budgets protect the result.
Sources and References
Facts follow Google web.dev.
- Fast sites (web.dev) web.dev
- Web Vitals (web.dev) web.dev