In 2021, Google made an announcement that shook the web industry: page speed is now an official Google ranking factor. The system Google uses to measure your page speed is called Core Web Vitals. If your site fails these tests, it ranks lower — no matter how good your content is.

The surprising truth is that images are responsible for over 50% of a webpage's total size. This means that simply by optimizing your images, you can dramatically improve your Core Web Vitals score and climb higher in Google search results.

What Are Core Web Vitals?

Core Web Vitals are three specific measurements Google uses to evaluate the user experience of your page:

Why WebP is the Best Format for Core Web Vitals

Google's own PageSpeed Insights tool will literally tell you: "Serve images in next-gen formats" — and WebP is that next-gen format. Here is why WebP wins:

• ✅ 30% smaller than JPEG at the same visual quality — directly improves LCP.
• ✅ 26% smaller than PNG — great for logos and icons with transparency.
• ✅ Supported by all modern browsers (Chrome, Firefox, Safari, Edge).
• ✅ Supports both lossy and lossless compression — use the right mode for each image.
• ✅ Supports animation (like GIF) but at much smaller sizes.

Step-by-Step: Fix Your Core Web Vitals with WebP

Step 1: Check Your Current Score

Go to pagespeed.web.dev, enter your website URL, and run the test. Look at the "Opportunities" section — if it says "Serve images in next-gen formats", you need WebP.

Step 2: Identify Which Images to Convert

Prioritize these images first (they have the biggest impact on LCP):

• Your header/hero image (the big banner at the top of the page).
• Product thumbnails on category pages.
• Any image that appears "above the fold" (visible without scrolling).

Step 3: Convert Images for Free

Use the free WebP Converter on naanji.com to convert your images instantly. No software installation needed. No uploads to external servers. Your images stay private.

💡 Pro Tip: Set the quality slider to 80% for photos (best balance between quality and file size) and 90% for product images where sharpness is critical.

Step 4: Replace Images on Your Website

For WordPress users: Upload the WebP image to your Media Library. WordPress 5.8+ supports WebP natively.

For Shopify users: Go to the product editor and replace the image directly.

For custom HTML sites: Replace the `src` attribute in your `img` tags.

Step 5: Advanced — Use the HTML Picture Tag

For maximum browser compatibility, use the HTML <picture> element. This serves WebP to browsers that support it, and falls back to JPEG for older browsers:

<picture>
  <source srcset="your-image.webp" type="image/webp">
  <img src="your-image.jpg" alt="Your image description">
</picture>

Real Results: What to Expect

Conclusion

Improving your Core Web Vitals does not require a developer or expensive tools. Converting your images to WebP is one of the highest-impact, lowest-effort changes you can make to your website. Start today, re-run your PageSpeed test after uploading the new images, and watch your score climb.