perf.cls-high

What to change

A finding of this rule on a page carries the exact edits for that page: the markup it quotes, and what to write instead.

When it runs

Runs with --lighthouse, on the command or the local server. A warning is a problem that costs a page ranking, clicks or citations. Each finding takes 5 points off the page's score.

The severity here is the rule's usual one: a finding can be raised or lowered when the page gives a reason.

Run it, or skip it

Check a page for this rule alone, after a fix for instance:

npx @rivi-software/agentic-seo-check audit https://example.com --lighthouse --rule perf.cls-high

Or from an assistant, with the MCP tool seo_audit_page:

{
  "url": "https://example.com",
  "lighthouse": true,
  "rules": [
    "perf.cls-high"
  ]
}

To leave it out of an audit, pass --disable perf.cls-high on the command, or disableRules: ["perf.cls-high"] to a tool.

• Infoperf.field-lcp-needs-improvementOn phones, real visits wait more than 2,500 ms for the largest element of the first screen at the 75th percentile: Largest Contentful Paint (LCP) in the Chrome UX Report's last 28 days, for the page's URL or, when it has too few visits, its origin. Google rates it as needing improvement.
• Infoperf.field-inp-needs-improvementOn phones, real visits wait more than 200 ms for the page to answer a tap or a key at the 75th percentile: Interaction to Next Paint (INP) in the Chrome UX Report's last 28 days, for the page's URL or, when it has too few visits, its origin. Google rates it as needing improvement.
• Infoperf.field-cls-needs-improvementOn phones, the layout of real visits shifts by more than 0.10 at the 75th percentile: Cumulative Layout Shift (CLS) in the Chrome UX Report's last 28 days, for the page's URL or, when it has too few visits, its origin. Google rates it as needing improvement.
• Warningperf.lcp-slowLargest Contentful Paint above 2.5 s (poor above 4 s). Lab measurement from Lighthouse.
• Warningperf.tbt-highTotal Blocking Time above 200 ms (poor above 600 ms). Lab proxy for Interaction to Next Paint.
• Infoperf.fcp-slowFirst Contentful Paint above 1.8 s (poor above 3 s).
• Warningperf.ttfb-slowServer response time (TTFB) above 800 ms.
• Warningperf.score-lowLighthouse performance score below 50.