Documentation
Everything you need to know about using our performance testing tool
Getting Started
Using our Core Web Vitals testing tool is simple and straightforward:
Enter your URL
Type or paste the full URL of the page you want to analyze (e.g., https://example.com).
Choose your device
Select whether you want to test for Mobile or Desktop users.
Click Analyze
Wait a few seconds while we analyze your page using the Google PageSpeed Insights API.
Review your results
Examine your Core Web Vitals scores and optimization recommendations.
Understanding Your Results
Your results include two types of data:
Field Data (Real-World)
Collected from real Chrome users visiting your site. This represents actual user experience.
Lab Data (Simulated)
Collected in a controlled environment using Lighthouse. Useful for debugging issues.
Metrics Explained
The three Core Web Vitals metrics measure different aspects of user experience:
LCP (Largest Contentful Paint)
Measures when the largest content element (image, video, or text block) becomes visible. A fast LCP tells users the page is useful.
INP (Interaction to Next Paint)
Measures how quickly the page responds to user interactions like clicks and taps. A low INP means the page feels responsive.
CLS (Cumulative Layout Shift)
Measures unexpected layout shifts. A low CLS means elements stay in place and don't jump around.
For a complete list of all performance metrics, visit our Glossary
Score Interpretation
The overall performance score is calculated based on weighted metrics:
Optimization Tips
Here are some general tips to improve your Core Web Vitals:
Optimize Images
Use modern formats (WebP, AVIF), compress images, and implement lazy loading for below-the-fold images.
Minimize JavaScript
Remove unused JavaScript, defer non-critical scripts, and break up long tasks to improve interactivity.
Reserve Space for Dynamic Content
Always specify dimensions for images, embeds, and ads to prevent layout shifts.
Use a Fast Hosting Provider
Consider using a CDN or edge caching solution like fast.site to reduce Time to First Byte (TTFB).