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Understanding Performance Grade
Table of Contents
The performance grade (0-100%) is calculated based on multiple factors:
- Load time > 3s: -5 points per second over
- TTFB > 600ms: -10 points
- Page size > 2MB: -5 points per MB over
- Requests > 50: -1 point per 10 requests over
- No compression: -10 points
- No caching headers: -5 points
Best Practices #
Optimize Images: Use modern formats (WebP, AVIF), compress images, and serve appropriately sized images for each device.
Enable Compression: Enable gzip or brotli compression on your server to reduce file sizes.
Minimize HTTP Requests: Bundle CSS and JavaScript files, use CSS sprites, and reduce external resources.
Use Caching: Set appropriate Cache-Control headers for static assets to reduce repeated downloads.
Optimize JavaScript: Code split, lazy load, and minify JavaScript. Avoid blocking the main thread with heavy operations.
Use a CDN: Serve static assets from a Content Delivery Network closer to your users.
Limitations #
– Cannot measure visual rendering or JavaScript execution time
– May not capture all lazy-loaded resources
– Results vary based on your network connection speed
– Tests run from your machine, not a remote server