Checklist SEO Manager

Core Web Vitals Optimization Checklist for SEO

Pass Core Web Vitals with this optimization checklist. Covers LCP, INP, and CLS with specific thresholds, diagnostic steps, and fix priorities.

Overview

Core Web Vitals are Google’s page experience metrics that directly influence search rankings. This checklist covers all three metrics — LCP, INP, and CLS — with specific diagnostic steps, fix priorities, and validation procedures.

Metric Thresholds

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

Target: All three metrics must be in the “Good” range at the 75th percentile of page loads (field data).

LCP Optimization Checklist

Server Response

TTFB (Time to First Byte) is under 800ms
Server-side rendering or static generation is in place
CDN is configured for all geographic regions
HTTP/2 or HTTP/3 is enabled
Server compression (gzip/Brotli) is active

Resource Loading

LCP element is identified (usually hero image or heading)
LCP image has fetchpriority="high" attribute
LCP image is NOT lazy loaded
LCP image uses <link rel="preload"> if not in initial HTML
LCP image is in modern format (WebP/AVIF) with appropriate compression
LCP image srcset provides correctly sized variants

Render Blocking

Critical CSS is inlined in <head>
Non-critical CSS is deferred with media attribute or loaded async
JavaScript is deferred or async (no render-blocking scripts)
Third-party scripts are loaded after LCP
Web fonts use font-display: swap or font-display: optional
Font files are preloaded: <link rel="preload" as="font">

INP Optimization Checklist

JavaScript Performance

Total JavaScript bundle size under 300 KB (compressed)
Long tasks (50ms+) are identified and broken up
Heavy computations use Web Workers
Event handlers are debounced/throttled where appropriate
requestAnimationFrame is used for visual updates
requestIdleCallback is used for non-urgent work

Input Responsiveness

Click handlers respond within 200ms
Form inputs have no perceptible lag
Dropdown menus open instantly
Navigation transitions are smooth
No JavaScript errors blocking interaction

Third-Party Scripts

Analytics scripts are loaded async
Chat widgets are lazy loaded
Ad scripts are deferred
Social embeds are loaded on interaction
Total third-party script impact is measured and acceptable

CLS Optimization Checklist

Images and Media

All <img> elements have explicit width and height attributes
All <video> and <iframe> elements have explicit dimensions
CSS aspect-ratio is set for responsive media containers
No images load without reserved space

Fonts

Web fonts use font-display: swap (or better, optional)
size-adjust is configured for fallback fonts to match web font metrics
Font files are preloaded to minimize swap time

Dynamic Content

No content injected above existing content after load
Cookie consent banners use fixed positioning (not push content)
Ad slots have reserved space with min-height
Lazy-loaded content has placeholder dimensions
No dynamically resizing elements in the viewport

Animations

CSS animations use transform and opacity only (no layout-triggering properties)
No top, left, width, height animations on visible elements
Transitions use will-change sparingly and appropriately

Diagnostic Tools

Tool	What It Measures	Data Type
Google PageSpeed Insights	All CWV	Lab + Field
Chrome UX Report (CrUX)	All CWV	Field (28-day)
Chrome DevTools Performance	All CWV	Lab
Web Vitals JS library	All CWV	Real User Monitoring
Google Search Console	All CWV	Field
Auditite	All CWV + page-level detail	Lab + monitoring

Page-Level Audit Worksheet

URL	LCP (s)	LCP Element	INP (ms)	CLS	Pass/Fail	Priority Fix

Fix Priority Order

Priority	Fix Category	Typical Impact
1	Server response time (TTFB)	Improves LCP across all pages
2	LCP image optimization	Directly improves LCP
3	Render-blocking resources	Improves LCP
4	Image dimension attributes	Directly fixes CLS
5	Font loading strategy	Fixes CLS + improves LCP
6	JavaScript optimization	Improves INP
7	Third-party script management	Improves INP + LCP
8	Dynamic content handling	Fixes CLS

Validation Process

Implement fixes on staging environment
Test with Chrome DevTools (lab data) — verify improvements
Deploy to production
Monitor field data in CrUX / Search Console (takes 28 days for full cycle)
Verify at 75th percentile threshold
Re-audit with Auditite to confirm all pages pass

Auditite monitors Core Web Vitals across every page on your site, alerting you when pages fall below thresholds and providing specific fix recommendations.

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