03 / WEB PERFORMANCE
Web performance
Treat loading, responsiveness and stability as part of the experience.
03. Measure the experience.
- Agree budgets for page weight, images, fonts and scripts before implementation.
- Serve appropriately sized, compressed images. Reserve their dimensions and lazy-load those below the fold, not the main hero image.
- Limit font families and weights. Review third-party scripts and avoid loading them without a clear need.
- Use Core Web Vitals to track loading, responsiveness and visual stability. Good thresholds are LCP at most 2.5 seconds, INP at most 200 milliseconds and CLS at most 0.1, assessed at the 75th percentile of visits.
- Combine laboratory checks with real-user measurements when available. A performance score alone is not an environmental assessment.
Standards & resources
These references inform the approach. They are not certifications or claims that every criterion has been audited on this site.
- RGESN: ecodesign of digital services, a framework for examining the service throughout its lifecycle.
- W3C Web Content Accessibility Guidelines 2.2, testable accessibility requirements.
- Core Web Vitals, user-experience performance metrics and thresholds.