Core Web Vitals Failed: Fix LCP, FID, CLS Issues

Digital Marketing

Feb 28, 2025

Learn how to fix Core Web Vitals issues like LCP, FID, and CLS to enhance user experience and improve search rankings.

Did you know 56% of websites fail Google's Core Web Vitals tests, which impacts search rankings and user experience? Here's what you need to fix:

  • LCP (Largest Contentful Paint): Improve load speed to under 2.5 seconds by optimizing images, reducing server response time, and minimizing JavaScript.

  • FID (First Input Delay): Achieve under 100ms by breaking up JavaScript tasks, deferring non-critical scripts, and using web workers.

  • CLS (Cumulative Layout Shift): Keep layout shifts below 0.1 by reserving space for images/ads, preloading fonts, and avoiding late-loading content.

Why it matters: Sites with strong Core Web Vitals see 24% lower abandonment rates and better SEO performance. Start with tools like PageSpeed Insights or Chrome DevTools to measure and fix your metrics.

Core Web Vitals Explained: How To Fix Site Optimization Issues

Core Web Vitals Basics

These metrics reveal why your site might not meet Google's performance standards.

LCP: Page Load Speed

Largest Contentful Paint (LCP) measures how fast the main content of your page is visible to users. Common causes of poor LCP include:

  • Slow server response times

  • Unoptimized images and media

  • Render-blocking JavaScript and CSS

  • Too many HTTP requests

Amazon found that revenue increased by 1% for every 100ms improvement in load time. This highlights why Google recommends keeping LCP under 2.5 seconds for a good score.

"Google has long tried to push pagespeed via Pagespeed Insights and AMP. And now with Core Web Vitals, it really has become inseparable from SEO." - Erwin Hofman, Pagespeed Consultant

FID: Page Response Time

First Input Delay (FID) measures how quickly your page responds to user actions, like clicks or taps. Poor FID is often caused by:

  • Heavy JavaScript blocking the main thread

  • Resource competition from third-party scripts

  • Delays from complex event handlers

  • Overloaded browser resources

Studies show 56% of websites fail Core Web Vitals assessments, often due to JavaScript-heavy pages. To achieve a good FID score, response times should be under 100 milliseconds. While responsiveness is critical, visual stability - tracked by CLS - also plays a key role in user experience.

CLS: Page Layout Stability

Cumulative Layout Shift (CLS) measures how stable your page layout is during loading. Poor CLS scores are often caused by:

| Issue | Effect on User Experience |
| --- | --- |
| Missing image dimensions | Elements shift as images load |
| Dynamic content insertion | Content pushes other elements down |
| Web font loading | Text moves during font swaps |
| Late-loading ads | Ads disrupt page layout

Mobile optimization is especially important, as 53% of mobile users abandon pages that take longer than 3 seconds to load. To meet Google's recommended CLS score of below 0.1, elements must stay stable throughout the loading process.

Google evaluates real-world data from users and requires that at least 75% of visitors have good Core Web Vitals for a site to pass its assessment.

Finding Core Web Vitals Problems

Identifying issues is just the beginning. To optimize your site effectively, you need to understand where and why these problems occur. Core Web Vitals issues require analysis of both lab and field data using diagnostic tools.

Measurement Tools Guide

Google offers several tools to measure Core Web Vitals performance, with PageSpeed Insights being one of the most widely used. It analyzes both lab and field data and provides a weighted scoring system for different metrics:

| Metric | Weight | Target Score |
| --- | --- | --- |
| Largest Contentful Paint (LCP) | 25% | < 2.5s |
| Cumulative Layout Shift (CLS) | 25% | < 0.1 |
| Total Blocking Time (TBT) | 30% | < 200ms |
| First Contentful Paint (FCP) | 10% | < 1.8s |
| Speed Index (SI) | 10% | <

Using DevTools, you can dive deeper by opening the Performance tab, recording a session while reloading your page, and identifying the 'LCP' marker in the Timings panel.

"PageSpeed Insights is the most misunderstood website performance testing tool on the planet. Core Web Vitals have a direct impact on search engine rankings whereas PageSpeed Insights shares helpful performance diagnostic information." - Ryan Sullivan, Chief of Staff, SiteCare

Once you have your metrics, the next step is identifying the specific causes of performance issues.

Locating Problem Elements

After measuring your metrics, focus on identifying the elements that are causing performance issues. Chrome DevTools simplifies this by directly highlighting LCP elements, making it easier to spot problem areas. To understand the root causes, you’ll need to consider both lab and field data:

Lab Data Benefits:

  • Provides instant feedback on changes.

  • Operates in a controlled testing environment.

  • Offers detailed diagnostic insights.

  • Results can be reproduced consistently.

Field Data Advantages:

  • Reflects real user experiences.

  • Accounts for actual device and network conditions.

  • Includes a 28-day history of performance.

  • Highlights geographic differences in performance.

"You might have to rethink your website. You need to figure out who's using your website, what their network conditions are, typical device, etc." - Ivailo Hristov, @NitroPack

Google tests from four global locations:

  • Northwestern US (Oregon)

  • Southeastern US (South Carolina)

  • Northwestern Europe (Netherlands)

  • Asia (Taiwan)

For the most accurate view of your site's performance, field data from the Chrome User Experience Report (CrUX) is invaluable. It captures real user interactions across various devices and networks, which directly affects search rankings and long-term optimization efforts.

Solutions for Failed Metrics

After diagnostics, apply these specific fixes to address each Core Web Vital metric. According to recent data, about 33% of websites worldwide still face challenges meeting Core Web Vitals standards, which impacts both search rankings and user experience.

Speed Up LCP Times

Improving LCP (Largest Contentful Paint) involves enhancing server response and resource delivery. Updates in WordPress 6.2 and 6.3 have shown performance boosts - block themes improved by 27%, and classic themes by 18%.

  • Server Optimization:

    • Reduce Time to First Byte (TTFB) to under 800 milliseconds

    • Implement effective caching

    • Use a CDN for content delivery

    • Remove unnecessary redirects

  • Resource Management:

    • Add fetchpriority="high" to LCP images

    • Use link rel="preload" for critical resources

    • Avoid lazy loading for LCP elements

    • Convert images to WebP format for better performance

"You can't just go and magically fix these things. You need to understand what the problem is itself - is it something on your page, or is it something more about how people are getting to your site." - Barry Pollard, @Google Chrome Team

Lower FID Scores

Aiming for an FID (First Input Delay) score of 100ms or less? These steps can help:

  • JavaScript Optimization:

    • Break long tasks into smaller chunks

    • Use web workers to handle background tasks

    • Implement code splitting to reduce initial load

    • Remove unused JavaScript

    • Compress files with GZIP or Brotli

  • Resource Loading:

    • Defer non-critical JavaScript

    • Optimize CSS delivery

    • Load polyfills only when needed

    • Minimize the impact of third-party scripts

Once interactivity is improved, address layout shifts to maintain visual stability.

Fix CLS Issues

CLS (Cumulative Layout Shift) measures visual stability, with a good score being less than 0.1. To prevent unexpected layout changes, follow these guidelines:

| Element Type | Best Practices |
| --- | --- |
| Images/Videos | Set explicit width and height attributes |
| Advertisements | Reserve fixed space using placeholders |
| Dynamic Content | Add new content below existing elements |
| Web Fonts | Preload fonts to ensure they’re ready for first paint |
| Animations | Use CSS transitions instead of animations when possible

For font optimization:

  • Host fonts locally

  • Use font-display: swap to prevent invisible text

  • Preload critical fonts for faster rendering

  • Reduce font file sizes to improve loading times

Maintaining Good Scores

Keeping Core Web Vitals in check requires consistent monitoring and timely fixes. Google Search Central emphasizes that good Core Web Vitals are key for both search performance and delivering a smooth user experience.

Regular Performance Checks

Stay ahead of potential issues by setting up monitoring systems. Here are some tools to help:

| Monitoring Tool | Purpose | Frequency |
| --- | --- | --- |
| Google Search Console | Analyze real-world usage data | Weekly |
| PageSpeed Insights | Run live performance tests | Bi-weekly |
| Chrome DevTools | Test during local development | On updates |
| <a href="https://github.com/GoogleChrome/lighthouse-ci" target="_blank" rel="nofollow noopener noreferrer" data-framer-link="Link:{"url":"https://github.com/GoogleChrome/lighthouse-ci","type":"url"}" data-framer-open-in-new-tab="">Lighthouse CI</a> | Perform automated checks | Every deployment |

"We highly recommend site owners achieve good Core Web Vitals for success with Search and to ensure a great user experience generally."
– Google Search Central

Be sure to validate performance before every launch to avoid setbacks.

Pre-Launch Testing

Use Lighthouse CI to test during both the build and deployment stages. Here's what to focus on:

  • Test performance on both mobile and desktop devices.

  • Measure the impact of new features on page speed.

  • Record baseline metrics to track improvements.

For example, Balloon Monkey's website initially showed poor Largest Contentful Paint (LCP) scores of 5.2 seconds during pre-launch testing. However, after implementing proper protocols, field data later showed passing Core Web Vitals scores.

Long-Term Success Plan

To maintain strong performance over time, you’ll need a structured approach. Here's a practical insight from the field:

"Once optimization is done, it's a good idea to create a process for adding new elements/content blocks on the website so that they won't hurt performance. A good example is adding Tweets via screenshots vs embeds: one of my experiments showed a difference of 11.5 seconds vs 1.9 seconds in unused JavaScript from just one embedded tweet that I replaced with a screenshot. Such processes will help make core web vitals optimization future proof."

Key actions for sustained success:

  • Monitor Core Web Vitals regularly using Search Console.

  • Test updates in a staging environment before deployment.

  • Keep all software components up to date.

  • Standardize how new content is added to the site.

  • Set performance benchmarks and review them periodically.

Maintaining Core Web Vitals is an ongoing effort - there’s no "set it and forget it" solution. Consistent monitoring and proactive tuning will ensure your site delivers great performance, boosting both search rankings and user satisfaction.

Conclusion

Websites that meet Core Web Vitals thresholds see a 24% drop in abandonment rates. Yet, most sites still fail at least one of these tests.

Looking at real-world examples, companies like Vodafone show how improvements can pay off. Their focused efforts led to:

  • 31% better LCP (Largest Contentful Paint) scores

  • 8% boost in sales

  • 15% higher lead-to-visit rates

  • 11% increase in cart-to-visit conversions

"Core Web Vitals are the subset of Web Vitals that apply to all web pages, should be measured by all site owners, and will be surfaced across all Google tools. Each of the Core Web Vitals represents a distinct facet of the user experience, is measurable in the field, and reflects the real-world experience of a critical user-centric outcome." - web.dev/vitals/

For businesses, improving Core Web Vitals doesn’t have to be overwhelming. Agencies like Visionary Marketing specialize in technical SEO and performance optimization, making it easier to achieve and maintain strong scores. These experts handle everything from initial fixes to ongoing monitoring, ensuring seamless improvements.

The stakes are high - 61% of users will switch to a competitor's site if they find a better experience. As Google continues to prioritize these metrics, keeping your Core Web Vitals in check is essential for staying visible in search results and retaining customers.

From identifying issues to implementing fixes and maintaining performance, every step shows your commitment to a better user experience. Regular monitoring and expert help can ensure your site delivers the speed and reliability that both users and Google expect.

‹ Ultimate Guide to Real-Time Keyword Tracking