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Core Web Vitals: How to Fix LCP, INP and CLS for Better SEO Rankings
Core Web Vitals measure how fast your pages load, how quickly they respond and how stable they are while loading. This guide explains each metric, the thresholds Google uses, and practical fixes, updated for Interaction to Next Paint (INP), which replaced First Input Delay in March 2024.
By Callan Pyfer, Founder & Lead SEO and GEO Strategist · May 20, 2025 · 8 min read
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Overview
What Are Core Web Vitals?
Core Web Vitals are three metrics Google uses to measure real-world user experience on a page: Largest Contentful Paint (LCP) for loading, Interaction to Next Paint (INP) for responsiveness and Cumulative Layout Shift (CLS) for visual stability. They are part of the page experience signals Google describes in its Core Web Vitals documentation.
Google measures them using field data from real Chrome users, collected in the Chrome User Experience Report. A page passes when at least 75 percent of visits meet the “good” threshold for each metric. Lab tools such as Lighthouse are useful for diagnosing problems, but the field data is what reflects your users’ actual experience.
How much do they matter for rankings? Google is clear that great page experience does not override relevance: a highly relevant page with average performance can still outrank a fast page that does not answer the query. But when competing pages are similar in relevance and quality, better experience can help, and faster, more stable pages almost always convert better.
Thresholds
Core Web Vitals Thresholds at a Glance
Thresholds from web.dev, measured at the 75th percentile of page loads:
| Metric | Measures | Good | Needs improvement | Poor |
|---|---|---|---|---|
| LCP | Loading: when the largest visible element renders | ≤ 2.5 s | 2.5–4.0 s | > 4.0 s |
| INP | Responsiveness: delay from interaction to visual update | ≤ 200 ms | 200–500 ms | > 500 ms |
| CLS | Visual stability: unexpected layout movement | ≤ 0.1 | 0.1–0.25 | > 0.25 |
First Input Delay (FID) was retired as a Core Web Vital in March 2024 and replaced by INP, which measures the responsiveness of all interactions on a page, not just the first.
LCP
How to Fix Largest Contentful Paint (LCP)
LCP is usually a hero image, a large heading or a banner. A slow LCP almost always comes from one of four places: a slow server response, render-blocking resources, a slow-loading LCP resource, or client-side rendering that delays the content. The web.dev LCP guide breaks these down in detail.
1. Speed up the Server Response
Measure Time to First Byte. Use caching, a content delivery network and efficient hosting, and avoid unnecessary redirects before the page loads.
2. Make the LCP Image Load First
Do not lazy-load the hero image. Lazy-load images below the fold instead. Give the hero image a high fetch priority, serve it in a modern format such as WebP or AVIF, size it correctly for each screen with srcset, and compress it.
3. Remove Render-Blocking Resources
Inline the small amount of CSS needed for the first screen, defer non-critical CSS and JavaScript, and remove unused code and plugins.
4. Avoid Rendering Critical Content with JavaScript
If the main content only appears after JavaScript runs, LCP suffers and crawlers may see less. Server-render or pre-render important content. Google’s JavaScript SEO basics explain how rendering affects search.
INP
How to Fix Interaction to Next Paint (INP)
INP measures how long a page takes to visually respond after someone clicks, taps or types. Poor INP usually means the browser’s main thread is busy running JavaScript when the user interacts. The web.dev INP guide covers diagnosis in depth.
- Break up long tasks. Split long-running JavaScript into smaller pieces so the browser can respond to input between them.
- Reduce JavaScript. Remove unused code, load features only when needed and avoid heavy frameworks for simple pages.
- Audit third-party scripts. Chat widgets, tag managers, ad and analytics scripts are frequent causes. Remove what you do not use and delay what you can.
- Keep event handlers light. Do the minimum work needed to show a response, then do the rest afterward.
- Avoid large DOM updates. Very large pages and complex layouts make every interaction slower to render.
CLS
How to Fix Cumulative Layout Shift (CLS)
CLS measures how much content moves unexpectedly while the page loads, such as text jumping when an image or ad appears. See the web.dev CLS guide for more detail.
- Set dimensions on images and video. Always include width and height attributes, or use CSS aspect-ratio, so the browser reserves space.
- Reserve space for ads and embeds. Give ad slots and embedded content a fixed minimum size.
- Do not insert content above existing content. Banners and notices should push nothing down after the page has started rendering, or should overlay instead.
- Load web fonts carefully. Preload key fonts and use font-display settings and fallback fonts with similar sizing to reduce text shifts.
- Animate with transforms. Use CSS transforms rather than properties that change layout.
Tools
Tools for Measuring Core Web Vitals
| Tool | Data type | Best for |
|---|---|---|
| PageSpeed Insights | Field (CrUX) and lab | Checking a single URL and getting specific recommendations |
| Search Console Core Web Vitals report | Field | Seeing which groups of pages pass or fail across your site |
| Chrome DevTools Performance panel | Lab | Diagnosing long tasks, render blocking and layout shifts |
| Lighthouse | Lab | Repeatable audits during development |
| Real user monitoring (RUM) | Field | Tracking your own users continuously, by page and device |
Common causes
The Most Common Core Web Vitals Problems We Find
In audits, the same handful of issues cause most failures across platforms:
| Problem | Metric affected | Typical fix |
|---|---|---|
| Oversized, uncompressed hero images | LCP | Resize, compress, serve WebP or AVIF and prioritize the hero image |
| Lazy-loading the hero image | LCP | Load the first-screen image eagerly; lazy-load only below the fold |
| Too many plugins or apps | LCP, INP | Remove unused plugins and apps, and replace heavy ones with lighter alternatives |
| Chat, tracking and ad scripts | INP, LCP | Audit third-party tags, remove unused ones and delay non-essential scripts |
| Images and embeds without dimensions | CLS | Add width and height or aspect-ratio to every image, video and iframe |
| Cookie and promo banners pushing content | CLS | Overlay banners instead of inserting them above content |
| Web fonts swapping late | CLS, LCP | Preload key fonts and use matched fallback fonts |
| Slow hosting or no caching | LCP | Enable page caching and a CDN, or upgrade hosting |
Action plan
A 30-Day Core Web Vitals Plan
Week 1: Find the Problem Pages
Open the Core Web Vitals report in Search Console, note which page groups fail and which metric is the problem, then test example URLs in PageSpeed Insights.
Week 2: Fix Templates, not Pages
Most issues come from shared templates: the header, hero, fonts or scripts used on every page. Fixing a template fixes every page that uses it.
Week 3: Tackle Scripts and Images
Remove unused plugins and third-party scripts, optimize hero images and reserve space for anything that loads late.
Week 4: Validate and Monitor
Use the Validate Fix option in Search Console, keep monitoring field data and add performance checks to your release process so problems do not return.
Mobile first
Why Mobile Performance Deserves Extra Attention
Google uses mobile-first indexing, which means it primarily uses the mobile version of your pages for indexing and ranking. Mobile devices also tend to have slower processors and less reliable connections than desktops, so pages that pass easily on desktop can fail on mobile.
When you test, always check mobile results first. Look at how your largest image is sized for small screens, how many scripts load before the first interaction is possible and whether anything shifts as fonts and banners load. Testing on a mid-range phone, not just a new flagship, gives a more realistic picture of what most visitors experience.
It is also worth checking your most important templates individually: the home page, service or product pages, location pages and blog posts. Each may have different causes, and fixing the template that receives the most search traffic usually delivers the biggest gains.
Beyond rankings
Why Performance Matters for AI Search and Conversions
Fast, stable pages help more than rankings. They reduce bounce rates, improve conversion rates and make it easier for crawlers, including AI crawlers, to fetch and process your content efficiently. Pages that rely on heavy client-side rendering can also be harder for some crawlers to read fully.
If your site has persistent performance issues, our Technical SEO Sprint fixes the biggest problems in a fixed 5–7 business day engagement, and our technical SEO services keep performance healthy over time.
Sources
Sources and Further Reading
Primary documentation and research referenced in this article:
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FAQ
Frequently Asked Questions
Are Core Web Vitals a ranking factor?
Yes, as part of Google’s page experience signals, but relevance and content quality matter far more. Good Core Web Vitals help most when competing pages are otherwise similar.
What replaced First Input Delay?
Interaction to Next Paint (INP) replaced First Input Delay as a Core Web Vital in March 2024. INP measures the responsiveness of all interactions on a page, not just the first one.
Why do PageSpeed Insights and Search Console show different results?
PageSpeed Insights shows both lab data from a single test and field data from real users, while Search Console reports field data grouped across similar pages. Field data is what Google uses for page experience.
How long does it take for fixes to show in Search Console?
Field data is collected over a rolling 28-day period, so improvements usually take several weeks to be fully reflected.
Do Core Web Vitals matter on mobile and desktop?
Yes. They are measured separately for mobile and desktop. Because Google uses mobile-first indexing, mobile performance deserves particular attention.
Can WordPress sites pass Core Web Vitals?
Yes. A lightweight theme, fewer plugins, optimized images, caching and careful handling of third-party scripts are usually enough for most WordPress sites to pass.
What is a good LCP score?
A good Largest Contentful Paint is 2.5 seconds or less for at least 75 percent of page visits.
What causes a poor INP score?
Usually too much JavaScript running on the main thread when someone interacts, often from third-party scripts, large frameworks or heavy event handlers.
Does a CDN help Core Web Vitals?
A CDN can improve server response times and LCP, especially for visitors far from your server, but it will not fix problems caused by heavy scripts or layout shifts.
Should I aim for a perfect PageSpeed score?
No. The lab score is a diagnostic tool. Focus on passing the Core Web Vitals thresholds in field data for real users, then on improvements that help conversions.
Can SEOMA fix Core Web Vitals for my site?
Yes. Our Technical SEO Sprint is a fixed-scope engagement of $750–$1,250 over 5–7 business days that addresses the biggest performance and crawlability issues.
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