THE RUBRIC
Page experience & performance
Whether the page is usable once it arrives.
Checks 12 9% of 129
Weight 8% of the overall score
Why it is weighted this way
The lightest category at 8%, deliberately. Performance is a real ranking input and a much smaller one than the industry implies. A fast page with nothing to say still has nothing to say.
What this category covers
- Largest Contentful Paint
- Interaction to Next Paint
- Cumulative Layout Shift
- Image sizing and lazy loading
- Render-blocking resources
- Mobile viewport and tap target sizing
Representative checks
A sample of what sits in this category, with how each one is decided and who is allowed to fix it. The full list of 129 lives in the product.
| Check | Method | Fix |
|---|---|---|
| Largest Contentful Paint Shipped. Measured from field or lab data depending on availability. | API | Assist |
| Interaction to Next Paint Shipped. | API | Assist |
| Cumulative Layout Shift Shipped. Most commonly caused by images without dimensions, which is an Auto fix. | API | Auto |
| Images sized and lazily loaded below the fold The cheapest performance win on most sites. | Rule | Auto |
What usually goes wrong
- Images without width and height, which is the most common cause of layout shift
- Render-blocking third-party scripts loaded before first paint
- Fonts fetched from a third-party CDN, adding two cross-origin round trips before text appears
- Tap targets too small or too close together on mobile
When these checks return unmeasured
A check in this category that cannot run is reported as unmeasured and counted in the denominator. It is never rounded up to a pass, which is the difference between a score that bounds its own claim and one that implies it examined everything.
- Field data is unavailable for a low-traffic page, so only lab data exists
- The third-party performance API was unavailable during the crawl
Where to start
- Add width and height to every image. Mechanical, and it usually fixes layout shift outright.
- Self-host fonts rather than fetching them at request time.
- Defer third-party scripts that do not need to run before first paint.