FitImage
FitImage / Guides / Fix "Serve Images in Next-Gen Formats"

Fix "Serve Images in Next-Gen Formats" in PageSpeed Insights

Guide

If you've run your site through Google PageSpeed Insights or Lighthouse and seen the warning "serve images in next-gen formats," it means some of your JPG or PNG images would load faster as WebP. The fix is genuinely simple — you don't need a plugin, a developer, or a CMS rebuild to clear it.

Why this warning shows up

WebP is a newer image format that typically produces files 25–35% smaller than an equivalent-quality JPG or PNG, with no visible difference for most photos and graphics. PageSpeed Insights flags any JPG or PNG it finds because switching would shrink the page's total download size and improve your Largest Contentful Paint (LCP) — one of Google's Core Web Vitals.

The fastest way to fix it without a plugin

  1. Identify the heaviest images PageSpeed Insights flagged — it usually lists them directly under the warning, with potential savings in KB.
  2. Open JPG to WebP (or PNG to WebP if your images are PNGs), and convert each flagged image. This runs entirely in your browser, so nothing is uploaded anywhere.
  3. Replace the original files in your site, CMS media library, or theme assets with the new .webp versions, updating the file references if your platform doesn't do this automatically.
  4. Re-run PageSpeed Insights to confirm the warning is gone and check your new load time.

What if a browser or plugin doesn't support WebP?

Virtually all current browsers (Chrome, Firefox, Safari, Edge) support WebP natively, but if you're worried about an older system or a tool that still needs JPG, keep both versions and serve WebP with a JPG fallback — most modern CMS platforms and CDNs can do this automatically once the WebP files exist.

This won't fix everything — and that's fine

Image format is one line item in a longer PageSpeed report. Render-blocking JavaScript, server response time, and unused CSS are separate issues with separate fixes. But images are usually the single biggest contributor to page weight, so this is often the highest-leverage five minutes you can spend on a slow page.

Fix it now: Convert your flagged images to WebP for free — Open JPG to WebP →

Frequently asked questions

What does "serve images in next-gen formats" actually mean?
It means Google PageSpeed Insights found JPG or PNG images on your page that would load faster as WebP (or AVIF). "Next-gen" just refers to newer image formats that compress more efficiently than JPG and PNG while looking the same.
Will converting to WebP actually fix my PageSpeed score?
It resolves that specific warning and usually shaves real load time off image-heavy pages, since WebP files are typically 25–35% smaller than equivalent JPGs. It won't fix every performance issue on its own — render-blocking scripts and server response time are separate problems — but it's one of the easier wins available.
Do I need a plugin or developer to do this?
No. You can convert each image to WebP yourself with a browser-based converter, then re-upload the WebP files wherever your JPGs or PNGs currently live — no plugin install, server access, or code change required for a one-time fix.