Core Web Vitals
- 758 installs
- 787 repo stars
- Updated June 9, 2026
- kostja94/marketing-skills
Core-web-vitals is an SEO technical skill that diagnoses and fixes LCP, INP, and CLS issues affecting Google Page Experience scores and search rankings for web developers.
About
Core-web-vitals is version 1.0.2 of a kostja94 marketing-skills agent skill focused on Google's Core Web Vitals user-experience metrics. It guides developers through diagnosing and fixing Largest Contentful Paint (LCP), Interaction to Next Paint (INP), and Cumulative Layout Shift (CLS)—confirmed ranking factors for both mobile and desktop search. The skill triggers on mentions of CWV, page speed, Page Experience, FID legacy terms, or performance regressions hurting rankings. Developers reach for core-web-vitals during ship-phase performance audits when Search Console or Lighthouse reports flag failing vitals and SEO traffic is at risk. For Google Search Console CWV-specific workflows, the skill directs pairing with the google-search-console skill.
- Optimizes LCP, INP, and CLS metrics with targeted technical guidance
- Provides exact Google thresholds and field-data explanations for each metric
- Covers both mobile and desktop ranking factors
- Integrates with Google Search Console workflows when CWV data is reported there
- Delivers actionable optimization steps without requiring deep frontend expertise
Core Web Vitals by the numbers
- 758 all-time installs (skills.sh)
- +6 installs in the week ending Jul 25, 2026 (Skillselion tracking)
- Ranked #612 of 1,879 Marketing & SEO skills by installs in the Skillselion catalog
- Security screen: LOW risk (skills.sh audit)
- Data as of Jul 31, 2026 (Skillselion catalog sync)
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| Installs | 758 |
|---|---|
| repo stars | ★ 787 |
| Security audit | 3 / 3 scanners passed |
| Last updated | June 9, 2026 |
| Repository | kostja94/marketing-skills ↗ |
How do you fix Core Web Vitals ranking issues?
Diagnose and fix Core Web Vitals issues that are hurting search rankings and page experience scores.
Who is it for?
Frontend and full-stack developers whose sites fail Core Web Vitals thresholds and need SEO-aligned performance remediation guidance.
Skip if: Skip core-web-vitals when performance is already green and the task is purely content strategy or link building.
When should I use this skill?
A developer mentions Core Web Vitals, CWV, LCP, INP, CLS, page speed, or Page Experience ranking problems.
What you get
Remediated LCP, INP, and CLS metrics with actionable performance fixes documented.
- CWV remediation plan
- LCP/INP/CLS fix recommendations
By the numbers
- Version 1.0.2 in kostja94/marketing-skills metadata
Files
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: 1. Tools: GSC Core Web Vitals report, PageSpeed Insights, Chrome DevTools 2. Metrics: Which metric is failing (LCP, INP, CLS) 3. 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
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Pick core-web-vitals over generic page-speed skills when failing CWV metrics directly threaten Google Page Experience rankings and you need LCP/INP/CLS-specific remediation.
FAQ
Which metrics does core-web-vitals cover?
Core-web-vitals covers Largest Contentful Paint (LCP), Interaction to Next Paint (INP), and Cumulative Layout Shift (CLS)—Google's confirmed Page Experience ranking factors for mobile and desktop search.
What version is the core-web-vitals skill?
The core-web-vitals skill is version 1.0.2 in the kostja94/marketing-skills repository, focused on diagnosing and fixing CWV issues that hurt search rankings and page experience scores.
Is Core Web Vitals safe to install?
skills.sh reports 3 of 3 security scanners passed. Review the Security Audits panel on this page before installing in production.