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Core Web Vitals Thresholds (February 2026)

Current Metrics

Metric Good Needs Improvement Poor
LCP (Largest Contentful Paint) ≤2.5s 2.5s–4.0s >4.0s
INP (Interaction to Next Paint) ≤200ms 200ms–500ms >500ms
CLS (Cumulative Layout Shift) ≤0.1 0.1–0.25 >0.25

Key Facts

  • INP replaced FID (First Input Delay) on March 12, 2024. FID was fully removed from all Chrome tools (CrUX API, PageSpeed Insights, Lighthouse) on September 9, 2024. INP is the sole interactivity metric.
  • Evaluation uses the 75th percentile of real user data (field data from CrUX).
  • Google assesses at the page level and the origin level.
  • Core Web Vitals are a tiebreaker ranking signal: they matter most when content quality is similar between competitors.
  • Thresholds unchanged since original definitions: ignore claims of "tightened thresholds" from SEO blogs.
  • December 2025 core update appeared to weight mobile CWV more heavily.
  • As of October 2025: 57.1% desktop sites and 49.7% mobile sites pass all three CWV.

LCP Subparts (February 2025 CrUX Addition)

LCP can now be broken into diagnostic subparts:

Subpart What It Measures Target
TTFB Time to First Byte (server response) <800ms
Resource Load Delay Time from TTFB to resource request start Minimize
Resource Load Time Time to download the LCP resource Depends on size
Element Render Delay Time from resource loaded to rendered Minimize

Total LCP = TTFB + Resource Load Delay + Resource Load Time + Element Render Delay

Use this breakdown to identify which phase is causing LCP issues.

Soft Navigations API (Experimental)

Chrome 139+ Origin Trial (July 2025): First step toward measuring CWV in SPAs.

  • Addresses the long-standing SPA measurement blind spot
  • Currently experimental, no ranking impact yet
  • Detects "soft navigations" (URL changes without full page load)
  • May affect future SPA CWV measurement

Detection: Check for SPA frameworks (React, Vue, Angular, Svelte) and warn about current CWV measurement limitations.

Measurement Sources

Field Data (Real Users)

  • Chrome User Experience Report (CrUX)
  • PageSpeed Insights (uses CrUX data)
  • Search Console Core Web Vitals report

Lab Data (Simulated)

  • Lighthouse
  • WebPageTest
  • Chrome DevTools

Field data is what Google uses for ranking. Lab data is useful for debugging.

Common Bottlenecks

LCP (Largest Contentful Paint)

  • Unoptimized hero images (compress, use WebP/AVIF, add preload)
  • Render-blocking CSS/JS (defer, async, critical CSS inlining)
  • Slow server response (TTFB >200ms: use edge CDN, caching)
  • Third-party script blocking (defer analytics, chat widgets)
  • Web font loading delay (use font-display: swap + preload)

INP (Interaction to Next Paint)

  • Long JavaScript tasks on main thread (break into smaller tasks <50ms)
  • Heavy event handlers (debounce, use requestAnimationFrame)
  • Excessive DOM size (>1,500 elements is concerning)
  • Third-party scripts hijacking main thread
  • Synchronous XHR or localStorage operations
  • Layout thrashing (multiple forced reflows)

CLS (Cumulative Layout Shift)

  • Images/iframes without width/height dimensions
  • Dynamically injected content above existing content
  • Web fonts causing layout shift (use font-display: swap + preload)
  • Ads/embeds without reserved space
  • Late-loading content pushing down the page

Optimization Priority

  1. LCP: Most impactful for perceived performance
  2. CLS: Most common issue affecting user experience
  3. INP: Matters most for interactive applications

Tools

# PageSpeed Insights API
curl "https://www.googleapis.com/pagespeedonline/v5/runPagespeed?url=URL&key=API_KEY"

# Lighthouse CLI
npx lighthouse URL --output json --output-path report.json

Performance Tooling Updates (2025)

  • Lighthouse 13.0 (October 2025): Major audit restructuring with reorganized performance categories and updated scoring weights. Lighthouse is a lab tool (simulated conditions): always cross-reference with CrUX field data for real-world performance.
  • CrUX Vis replaced the CrUX Dashboard (November 2025). The old Looker Studio dashboard was deprecated. Use CrUX Vis or the CrUX API directly.
  • LCP subparts added to CrUX (February 2025): Time to First Byte (TTFB), resource load delay, resource load time, and element render delay are now available as sub-components of LCP in CrUX data.
  • Google Search Console 2025 features (December 2025): AI-powered configuration for automated analysis. Branded vs. non-branded queries filter. Hourly data available in API. Custom chart annotations. Social channels tracking.

Mobile-first indexing is 100% complete as of July 5, 2024. Google now crawls and indexes ALL websites exclusively with the mobile Googlebot user-agent. Ensure your mobile version contains all critical content, structured data, and meta tags.