kostja94/core-web-vitals
skills/seo/technical/core-web-vitals/SKILL.md
When the user wants to optimize Core Web Vitals, fix LCP, INP, or CLS issues. Also use when the user mentions "Core Web Vitals," "CWV," "LCP," "INP," "CLS," "FID," "page speed," "page performance," "Largest Contentful Paint," "Interaction to Next Paint," "Cumulative Layout Shift," or "Page Experience." For GSC CWV, use google-search-console.
$ install --global
skillsauthnpx skillsauth add kostja94/marketing-skills core-web-vitalsInstall this skill globally with one command. Works with Claude Code, Cursor, and Windsurf.
Security Scan Results
3 of 9 scanners reported clean
Some scanners were skipped, did not run, or reported a non-clean status. Review each row below.
3
Scanners Passed
9
Scanners in report
Clean
TrivyContainer and dependency vulnerability scanner
95%
Clean
SemgrepStatic code analysis for vulnerabilities
95%
Clean
mcp-scan (Snyk)Model Context Protocol security validation
95%
Skipped
Snyk (dep)Open source security scanning
50%
Skipped
Socket.devSupply chain security analysis
50%
Skipped
VirusTotalMulti-engine malware detection
50%
Skipped
CrowdStrikeAdvanced threat intelligence
50%
Skipped
OSV-ScannerOpen Source Vulnerability database check
50%
Skipped
OWASP Dep-Check
50%
Last scanned: May 6, 2026, 7:55 AM144.6s1 file scanned
SKILL.md
- name:
- core-web-vitals
- description:
- When the user wants to optimize Core Web Vitals, fix LCP, INP, or CLS issues. Also use when the user mentions "Core Web Vitals," "CWV," "LCP," "INP," "CLS," "FID," "page speed," "page performance," "Largest Contentful Paint," "Interaction to Next Paint," "Cumulative Layout Shift," or "Page Experience." For GSC CWV, use google-search-console.
- version:
- 1.0.2
SEO Technical: Core Web Vitals
Guides optimization of Core Web Vitals (CWV)—Google's user experience metrics that affect search ranking. CWV are confirmed ranking factors for mobile and desktop.
When invoking: On first use, if helpful, open with 1–2 sentences on what this skill covers and why it matters, then provide the main output. On subsequent use or when the user asks to skip, go directly to the main output.
Scope (Technical SEO)
- LCP (Largest Contentful Paint): Loading performance; time to render largest content element
- INP (Interaction to Next Paint): Responsiveness; replaced FID on March 12, 2024
- CLS (Cumulative Layout Shift): Visual stability; unexpected layout shifts
Target Thresholds (75th percentile, field data)
| Metric | Target | Good | Needs Improvement | Poor | |--------|--------|------|-------------------|------| | LCP | ≤2.5s | ≤2.5s | 2.5–4.0s | >4.0s | | INP | ≤200ms | ≤200ms | 200–500ms | >500ms | | CLS | <0.1 | ≤0.1 | 0.1–0.25 | >0.25 |
Source: Google Page Experience
Initial Assessment
Check for project context first: If .claude/project-context.md or .cursor/project-context.md exists, read it for site URL.
Identify:
- Tools: GSC Core Web Vitals report, PageSpeed Insights, Chrome DevTools
- Metrics: Which metric is failing (LCP, INP, CLS)
- Page type: Hero, article, product, list—LCP candidate differs
LCP Optimization
LCP measures the time until the largest content element (image, video, or text block) is visible.
| Cause | Fix |
|-------|-----|
| Slow server response | Reduce TTFB; use CDN; optimize server |
| Render-blocking resources | Defer non-critical CSS/JS; inline critical CSS |
| Large images | WebP/AVIF; compress; width/height to prevent CLS; see image-optimization |
| Client-side rendering | SSR/SSG for above-fold content; see rendering-strategies |
| Third-party scripts | Load async; defer non-critical |
LCP candidates: Hero image, large text block, video poster. Ensure above-fold images use loading="eager" (default); never lazy-load LCP.
INP Optimization
INP measures responsiveness—time from user interaction to next paint. Replaced FID on March 12, 2024.
| Cause | Fix |
|-------|-----|
| Long-running JS | Break tasks >50ms; use requestIdleCallback; Web Workers |
| Heavy event handlers | Debounce/throttle; defer non-critical work |
| Main thread blocking | Reduce third-party scripts; defer non-critical JS |
| Layout thrashing | Batch DOM reads/writes; avoid forced reflows |
CLS Optimization
CLS measures unexpected layout shifts.
| Cause | Fix |
|-------|-----|
| Images without dimensions | Always set width and height attributes |
| Dynamic content | Reserve space for ads, embeds; use min-height |
| Web fonts | font-display: optional or swap; preload critical fonts |
| Animations | Use transform instead of top/left/width |
Reserve space: For images, ads, embeds—define dimensions before load. Avoid inserting content above existing content without reserved space.
Tools & Monitoring
| Tool | Use | |------|-----| | GSC | Core Web Vitals report; URL grouping; field data | | PageSpeed Insights | Lab + field data; mobile + desktop | | Chrome DevTools | Performance panel; LCP element; layout shift overlay |
Output Format
- Current state: Which metrics fail (LCP, INP, CLS)
- Prioritized fixes: By impact
- References: Web Vitals, Page Experience
Related Skills
- image-optimization: LCP image optimization; WebP; lazy loading (below-fold only)
- google-search-console: CWV report; field data monitoring
- mobile-friendly: Mobile-first indexing; mobile CWV targets
- rendering-strategies: SSR/SSG for LCP; content in initial HTML
- site-crawlability: Redirect chains waste crawl; fix for performance
Related Skills
kostja94/twitter-cards
data-ai
VerifiedTrustedCommunity
When the user wants to add or optimize Twitter Card metadata for X (Twitter) link previews. Also use when the user mentions "Twitter Card," "twitter:card," "twitter:image," "twitter:title," "X preview," or "tweet preview." For Facebook/LinkedIn previews, use open-graph.
571SKILL.mdUpdated Apr 24, 2026
kostja94/open-graph
testing
VerifiedTrustedCommunity
When the user wants to add or optimize Open Graph metadata for social sharing. Also use when the user mentions "Open Graph," "og:tags," "og:title," "og:image," "og:description," "Facebook preview," "LinkedIn preview," or "social share preview." For X (Twitter) link previews, use twitter-cards. For SERP title/description, use title-tag and meta-description.
571SKILL.mdUpdated Apr 24, 2026
kostja94/terms-page-generator
tools
VerifiedTrustedCommunity
When the user wants to create, optimize, or structure Terms of Service page. Also use when the user mentions "terms of service," "terms and conditions," "terms of use," "user agreement," "ToS," "legal terms," "service agreement," or "terms page." For legal overview page, use legal-page-generator.
571SKILL.mdUpdated Apr 24, 2026
kostja94/shipping-page-generator
development
VerifiedTrustedCommunity
When the user wants to create or optimize a shipping or delivery information page. Also use when the user mentions "shipping," "delivery," "shipping policy," "delivery times," "shipping page," "free shipping," "shipping rates," "delivery options," "shipping info," "cross-border shipping," "international delivery," or "order tracking." For legal overview, use legal-page-generator.
571SKILL.mdUpdated Apr 24, 2026