How to Fix “Serve Images in Next-Gen Formats” in PageSpeed Insights

November 29, 2025

If you’ve run your website through Google PageSpeed Insights, you’ve likely seen the warning: “Serve images in next-gen formats”. This is one of the most common opportunities to improve your site’s performance score and Core Web Vitals.

But what does it mean, and how do you fix it without buying expensive plugins or software?

What Are “Next-Gen” Formats?

For decades, the web ran on JPEG and PNG. While reliable, these formats were created long before the modern mobile web.

“Next-gen” formats like WebP (developed by Google) and AVIF (the newest standard) are designed specifically for the web. They offer:

• Superior Compression: Often 30-50% smaller than comparable JPEGs.
• High Quality: Less visible artifacting at lower file sizes.
• Transparency Support: WebP supports transparency just like PNG, but at a fraction of the size.

Google wants you to use these formats because they load faster, use less data, and improve the user experience.

Why You Should Fix This Warning

Ignoring this warning hurts your site in two ways:

1. Slower Load Times: Larger files mean your LCP (Largest Contentful Paint) metric suffers.
2. Lower SEO Rankings: Since page speed is a ranking factor, unoptimized images can drag down your position in search results.

The Solution: Convert to WebP or AVIF

You don’t need to be a developer to fix this. You just need to convert your existing images.

Step 1: Identify the Problem Images

Look at your PageSpeed Insights report. It will list the specific image URLs that are slowing you down.

Step 2: Convert with MiniJPG

You can use MiniJPG to convert your images for free, directly in your browser.

1. Select “WebP” or “AVIF” from the Output Format dropdown.
2. Drag and drop your JPEGs or PNGs into the tool.
3. Download the converted files.

Tip: WebP is supported by almost all browsers (96%+). AVIF offers even better compression but has slightly less support (though it’s growing fast).

Step 3: Update Your Website

Replace the old .jpg or .png files on your server or CMS with the new .webp or .avif versions.

If you are using HTML, you can use the <picture> tag to provide a fallback for very old browsers:

<picture>
  <source srcset="image.avif" type="image/avif">
  <source srcset="image.webp" type="image/webp">
  <img src="image.jpg" alt="My optimized image">
</picture>

Conclusion

Fixing the “Serve images in next-gen formats” warning is a quick win for your SEO and user experience. By switching to WebP or AVIF, you can drastically reduce your bandwidth usage and speed up your site.

Ready to optimize? Head over to MiniJPG and start converting your library today.