If you’ve ever run your site through PageSpeed Insights and seen the warning “Serve images in next-gen formats,” you’re not alone. It’s one of the most common flags Google throws at websites, and honestly, the wording doesn’t explain much. What is a “next-gen format”? Why does Google care? And how do you actually fix it without hiring a developer?
Let’s clear all of that up.
What “Next-Gen Image Formats” Actually Means
For years, the web ran almost entirely on JPG and PNG images. Both formats work fine, but they were designed decades ago, long before anyone was loading pages on a phone over patchy mobile data. They compress images in ways that leave a lot of file size on the table.
“Next-gen” formats — mainly WebP, and more recently AVIF — were built specifically to shrink image file sizes without a noticeable drop in quality. When Google’s tools mention next-gen formats, they’re almost always talking about WebP, since it has the widest browser support and the easiest path to adoption.
Why Google Flags This At All
Page speed is a ranking factor, and images are usually the heaviest part of any webpage. A single unoptimized PNG can be 3-4x larger than it needs to be. Multiply that across a dozen images on a page, and you’ve got a site that loads slowly on mobile, which hurts both user experience and your Core Web Vitals scores.
Google isn’t being picky for no reason — smaller images genuinely make pages load faster, and PageSpeed Insights is just surfacing an easy, high-impact fix.
How Much Does This Actually Save?
In most real-world cases, converting standard JPG or PNG images to WebP cuts file size by 25-35% with no visible quality loss. For image-heavy pages — blogs, portfolios, ecommerce product pages — that can mean shaving a full second or more off load time.
How to Fix the “Next-Gen Formats” Warning
You don’t need a build pipeline or a WordPress plugin to do this. The fastest way is to convert your existing images directly:
- Gather the images PageSpeed Insights flagged (it usually lists them by name in the report).
- Run them through a Free Image to WebP Converter — you can batch-convert several at once instead of doing them one by one.
- Replace the old JPG/PNG files in your media library or file system with the new WebP versions.
- Re-run PageSpeed Insights to confirm the warning is gone.
That’s it. No code changes, no plugin installs required if you’re comfortable swapping files manually.
A Quick Note on Compatibility
WebP has been supported by all major browsers for years now, so compatibility isn’t really a concern the way it used to be. If you want a belt-and-suspenders approach, some site owners keep a JPG fallback for very old browsers, but for the vast majority of traffic, straight WebP is fine.
What About AVIF?
AVIF compresses even better than WebP in some cases, but support and tooling are still catching up, and the compression process is noticeably slower. For most sites, WebP is the practical, well-supported choice today. If you want to read more about the technical differences, MDN’s guide to image file types is a solid reference.
Wrapping Up
The “next-gen image formats” warning sounds more complicated than it is. In practice, it just means: your images are bigger than they need to be, and there’s a well-supported format that fixes that. Convert them once, replace the files, and you’ve knocked out one of the most common PageSpeed complaints in a single pass.
If you’re cleaning up other performance warnings while you’re at it, you might also want to look at minifying your CSS and JavaScript — it’s the same idea: strip out what your browser doesn’t need, and the page loads faster.
Convert your images now with the free Image to WebP Converter — no signup, batch upload supported.
