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Rule · Performance and mobile

Core Web Vitals meet the "good" thresholds in field data

SEO-PERF-01C2 Recommended· w4

Class
C2 Recommended
Weight
4
Severity on fail
major
Applies to
Google

Scope and evidence

Evaluated on (origin or member of P, form factor) pairs with data, for the form factors PHONE and DESKTOP only. The book marks this requirement DOCUMENTED RECOMMENDATION, DOCUMENTED SIGNAL. It needs crux; without that input the rule reports as not evaluated rather than guessing.

{scope_label} is "the origin {origin}" or "{url}". {bing_clause} is " Bing lists page load time among its main ranking parameters." when Bing is a selected engine, otherwise empty. The book's SEO-PERF-02 (Bing page load time) is folded into this rule's reason. No CrUX data means not_evaluated, not failure: field data requires a page to be publicly discoverable and sufficiently popular, and "An exact number is not disclosed" (CRUX-METHOD). Lab tools (Lighthouse, PageSpeed lab scores) are never scored: their results vary between runs, and Google says chasing a perfect score for SEO "may not be the best use of your time" (G-PAGE-EXP, §6). The MS-BING-RANK citation is emitted only when Bing is a selected engine.

Fail conditions

Each condition has a stable code and a reason template. The evaluator fills the placeholders from observed values only; no sentence in a report is generated.

  • lcp_over

    In Chrome UX Report field data for {scope_label} ({form_factor}, collection period {first_date} to {last_date}), {metric} at the 75th percentile is {value}, above the 'good' threshold of {threshold}. Google documents Core Web Vitals as used by its ranking systems, without a published weight.{bing_clause}

  • inp_over

    In Chrome UX Report field data for {scope_label} ({form_factor}, collection period {first_date} to {last_date}), {metric} at the 75th percentile is {value}, above the 'good' threshold of {threshold}. Google documents Core Web Vitals as used by its ranking systems, without a published weight.{bing_clause}

  • cls_over

    In Chrome UX Report field data for {scope_label} ({form_factor}, collection period {first_date} to {last_date}), {metric} at the 75th percentile is {value}, above the 'good' threshold of {threshold}. Google documents Core Web Vitals as used by its ranking systems, without a published weight.{bing_clause}

The documented fix

Work on the specific metric (server response and resource priority for LCP; main-thread work for INP; reserved space for media and embeds for CLS).

Sources, quoted

These are the passages the rule rests on, stored once in the knowledge base and emitted exactly as written. A citation marked for specific conditions appears only on findings with those codes.