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20 checks · 22% of the score

Performance checks

How fast the page loads and becomes usable, from Google's Lighthouse run and from real Chrome users where there are enough of them. 8 of these have a page of their own; every one is listed here with the severity it carries and when it is skipped.

Every check in this category

20
  • high

    Largest Contentful Paint (LCP)

    Reports: Largest Contentful Paint is slow.

    Medium over 2.5s, high over 4s.

    Skipped, and not counted either way, when the Lighthouse run from PageSpeed Insights is unavailable.

    performance-lcp

  • high

    Cumulative Layout Shift (CLS)

    Reports: Cumulative Layout Shift is high.

    Medium over 0.1, high over 0.25.

    Skipped, and not counted either way, when the Lighthouse run from PageSpeed Insights is unavailable.

    performance-cls

  • high

    Total Blocking Time (TBT)

    Reports: Total Blocking Time is high.

    Medium over 200ms, high over 600ms. The lab-measurable stand-in for INP.

    Skipped, and not counted either way, when the Lighthouse run from PageSpeed Insights is unavailable.

    performance-tbt

  • high

    Page load time is slow

    Medium over 3s, high over 6s. No official threshold exists for this one; these follow the usual web-perf convention.

    performance-load-time

  • medium

    Speed Index is slow

    Medium over 3.4s, high over 5.8s.

    Skipped, and not counted either way, when the Lighthouse run from PageSpeed Insights is unavailable.

    performance-speed-index

  • medium

    Time to First Byte

    Reports: Time to First Byte is slow.

    Medium over 800ms, high over 1.8s.

    performance-ttfb

  • medium

    First Contentful Paint is slow

    Medium over 1.8s, high over 3s.

    performance-fcp

  • high

    Real users see slow Largest Contentful Paint

    Chrome's 75th percentile over the trailing 28 days.

    Skipped, and not counted either way, when Chrome has too little real-user traffic for the origin to report.

    performance-field-lcp

  • high

    Real users see slow Interaction to Next Paint

    Over 200ms at the 75th percentile. INP, not the retired FID.

    Skipped, and not counted either way, when Chrome has too little real-user traffic for the origin to report.

    performance-field-inp

  • high

    Real users see high Cumulative Layout Shift

    Over 0.1 at the 75th percentile.

    Skipped, and not counted either way, when Chrome has too little real-user traffic for the origin to report.

    performance-field-cls

  • medium

    Real users see slow Time to First Byte

    Over 800ms at the 75th percentile.

    Skipped, and not counted either way, when Chrome has too little real-user traffic for the origin to report.

    performance-field-ttfb

  • medium

    Large page weight

    Over 3MB transferred.

    performance-page-weight

  • low

    High request count

    Over 100 requests.

    performance-request-count

  • medium

    Text compression

    Reports: Text resources served without compression.

    performance-compression

  • medium

    Render-blocking resources

    Reports: Render-blocking resources in the document head.

    performance-render-blocking

  • low

    Cache headers on static assets

    Reports: Static assets missing cache headers.

    performance-cache-headers

  • low

    Modern image formats

    Reports: Images served as PNG or JPEG with no WebP or AVIF anywhere.

    performance-modern-images

  • low

    High DOM node count

    Over 1500 elements.

    performance-dom-node-count

  • low

    JavaScript appears unminified

    performance-js-minified

  • low

    CSS appears unminified

    performance-css-minified

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