Lighthouse Performance Score
The industry standard for measuring web performance. Understanding these metrics is crucial for optimizing user experience and SEO.
Performance Metrics (Core Web Vitals)
Largest Contentful Paint measures loading performance. It marks the point in the page load timeline when the page's main content has likely loaded.
Interaction to Next Paint observes the latency of all user interactions (clicks, taps, and keyboard inputs) throughout the lifespan of a user's visit.
Cumulative Layout Shift measures visual stability. It quantifies how much elements move around on the page as it loads.
Total Blocking Time measures the total amount of time that a page is blocked from responding to user input, such as mouse clicks.
Speed Index shows how quickly the contents of a page are visibly populated.
The Lighthouse Report Structure
1. Performance Score (0-100)
A weighted average of the metric scores. 90-100 is Green, 50-89 is Orange, and 0-49 is Red.
2. Opportunities
Suggestions that can help your page load faster. These don't directly affect your Performance score, but improving them usually improves your metrics.
- Eliminate render-blocking resources
- Properly size images
- Defer offscreen images
3. Diagnostics
More information about the performance of your application. These checks ensure you adhere to web development best practices.
- Ensure text remains visible during webfont load
- Reduce the impact of third-party code
Categories & Aspects
Lighthouse runs separate tests for Mobile and Desktop. Mobile scores are usually lower because it simulates a slower 4G connection and a mid-tier device (Moto G4).
Beyond performance, Lighthouse checks for basic SEO (title tags, meta descriptions) and Accessibility (color contrast, ARIA labels).