Google changed the rules of the game with Core Web Vitals. These metrics measure how users experience the speed, responsiveness, and visual stability of your website. If your site fails these tests, your search engine rankings will suffer. Many business owners think they are doing everything right but still see red marks in their Google Search Console.

We see the same errors repeated across many industries. Most of these mistakes happen because people focus on how a site looks rather than how it performs technically. Performance is no longer an afterthought. It is a core requirement for digital marketing success

Here are the 7 biggest mistakes you are likely making with your Core Web Vitals and exactly how you can fix them today

1. Uploading Raw Unoptimized Images

The biggest killer of Largest Contentful Paint (LCP) is unoptimized images. LCP measures how long it takes for the largest element on the screen to load. Usually, this is a hero image or a large banner. If you upload a 5MB photo straight from a camera or a stock site, you are forcing your user's browser to work too hard.

Many sites use high-resolution PNGs or JPEGs that are far larger than the container they sit in. This creates massive bloat. Even if the image looks small on the screen, the browser still has to download every single pixel.

How to Fix It

• Switch to modern formats like WebP or AVIF which offer better compression than JPEG
• Use responsive image tags so the browser only downloads the size it needs for that specific device
• Implement lazy loading for images that are not immediately visible on the screen
• Compress every image before it goes live on your web design

2. Choosing Cheap or Poorly Configured Hosting

Your Time to First Byte (TTFB) is the foundation of your site speed. If your server is slow to respond, every other metric will be delayed. You cannot have a fast LCP if your server takes a full second just to acknowledge a request. Many businesses try to save money by using shared hosting plans that are overcrowded and slow.

Poor server configuration also leads to issues with caching. If your server does not tell the browser to "remember" certain files, the browser has to download everything from scratch every time a user clicks a new page.

How to Fix It

• Move your site to a high-performance web hosting provider
• Enable server-level caching to serve pages faster
• Use a Content Delivery Network (CDN) to host your files closer to your users
• Upgrade your PHP version to the latest stable release to improve processing speed

3. Overloading the Browser with Custom Fonts

Fonts are often overlooked as a performance killer. Every custom font weight and style you add is another file the browser must fetch. If you use four different weights of a custom Google Font, you are adding hundreds of kilobytes to your page weight.

Even worse, if the font loads slowly, the browser might hide the text until the font is ready. This is called "Flash of Unseen Text." Or, it might show a default font and then "snap" to the custom font, causing a layout shift that ruins your Cumulative Layout Shift (CLS) score.

How to Fix It

• Limit your site to two custom fonts at most
• Only load the specific weights you actually use on the site
• Use the font-display: swap CSS property to show text immediately using a system font
• Preload your most important font files so they are the first things the browser looks for

4. Neglecting JavaScript Execution Times

JavaScript is usually what makes a website interactive, but too much of it will paralyze your site. This affects Interaction to Next Paint (INP), which is the metric that replaced First Input Delay (FID). If your site has a lot of "heavy" scripts running, the browser cannot respond when a user clicks a button or opens a menu.

We often find that sites have "zombie" code. This is code from old tracking pixels, deleted plugins, or features that no longer exist. This code still runs in the background and eats up processing power.

How to Fix It

• Audit your site and remove any plugins or third-party scripts you do not use
• Minify your JavaScript to reduce file sizes
• Defer non-essential scripts so they load after the main content is visible
• Consider custom web development to replace heavy plugins with lightweight code

5. Running Third-Party Scripts Above the Fold

Third-party scripts are things like chat widgets, ad networks, and social media feeds. These are notorious for being slow. If you place these scripts at the top of your page code, the browser stops everything else to deal with them. This "render-blocking" behavior keeps your users staring at a white screen.

Ads are a primary culprit for layout shifts. If an ad container doesn't have a defined size, it will suddenly pop into view and push your content down. This is a frustrating experience and a major Core Web Vitals failure.

How to Fix It

• Move non-essential third-party scripts to the footer of your site
• Use a tag manager to control when and how scripts fire
• Hard-code the dimensions of ad slots so the page does not jump when they load
• Delay chat widgets until after the user has scrolled or interacted with the page

6. Failing to Define Image and Element Dimensions

Cumulative Layout Shift (CLS) is often the hardest metric to fix because it requires attention to detail. A common mistake is leaving out the width and height attributes on images and video embeds. When the browser doesn't know how big an image is, it assumes the size is zero until the image finishes downloading. Once it finishes, the content below it "jumps" down to make room.

This also happens with dynamic content like "related posts" sections or newsletter sign-up bars that slide in after the page loads.

How to Fix It

• Always include width and height attributes in your HTML tags
• Use CSS aspect-ratio boxes to reserve space for dynamic content
• Avoid inserting new content above existing content unless it is in response to a user action
• Check your site's visual stability on mobile devices specifically

7. Only Testing the Homepage

This is perhaps the most dangerous mistake. Many people run a test on their homepage, see a green score, and assume the whole site is perfect. However, your service pages, blog posts, and contact pages often have different layouts and different performance issues.

Google collects data from real users across your entire site. If your blog posts are slow because of large images, your overall "passed" status can be revoked even if your homepage is lightning fast. You need a comprehensive strategy for site-wide performance.

How to Fix It

• Test at least five different types of pages on your site
• Use the Core Web Vitals report in Google Search Console to see which URLs are failing
• Monitor mobile performance separately from desktop performance
• Regularly check for "regressions" after you update your site or add new content

Summary Checklist for Better Scores

Fixing Core Web Vitals is not a one-time task. It is an ongoing process of keeping your site lean and efficient. We suggest you start with these steps every time you add a new page:

1. Compress all images and use WebP format
2. Assign specific heights and widths to every image and video
3. Limit the use of external fonts and pre-load them
4. Check for render-blocking JavaScript in the header
5. Test the page on a mobile device using a slow connection

If you find that your current platform is too slow to meet these standards, it may be time for a more professional approach. We help businesses build sites that are both beautiful and technically sound. You can see examples of high-performing sites in our portfolio

Don't let technical errors hold back your growth. Address these mistakes today and you will see better rankings and happier users. If you need help diagnosing a specific issue, our team is available for support

Ready to get started on a faster website? Contact us to discuss your project. We can help you turn those red scores into green ones and ensure your business stays competitive in the digital landscape.