How to Fix: Images use AVIF

Images use AVIF is an important SEO check in the Site Performance & Core Web Vitals category. This is a lower-priority optimization. Address it after handling more critical issues.

AVIF is the current frontrunner in the long race to make images weigh less. It typically beats both JPEG and WebP on file size at the same visual quality, and since images are usually the heaviest thing on a page, that translates directly into faster loads and better Core Web Vitals. It sits correctly in the lower-priority tier — you should fix your layout shifts and oversized images first — but once the fundamentals are sorted, AVIF is a clean, mechanical win.

What this check is really testing

Whether your site serves images in AVIF (or at least modern next-gen formats) to browsers that support it, rather than shipping heavy legacy JPEG and PNG to everyone. Crucially, it is also implicitly testing whether you do this with a fallback, so browsers that do not yet support AVIF still receive a format they can render. Format adoption without a fallback is a bug, not an optimisation.

Why this matters for SEO

• Smaller image files improve Largest Contentful Paint, a Core Web Vitals metric that feeds ranking.
• Lighter pages load faster on mobile and slow connections, cutting bounce and lifting conversion.
• PageSpeed Insights explicitly flags “Serve images in next-gen formats” — this closes that item.
• Less bandwidth per visit means lower hosting and CDN costs at scale.

A word from someone who has chased image formats before

I have been exporting graphics into “the format that will win” since the early nineties, and it has taught me one durable habit: always keep the fallback. In CorelDRAW and Aldus FreeHand I watched a parade of formats promise to be the standard and then fade — everyone had a preferred export, none of them read everywhere, and the safe move was always to hold a universally readable version alongside the clever new one. AVIF is simply the latest entry in that parade. It is genuinely better, and I would adopt it. But I would no more serve AVIF with no JPEG fallback than I would have shipped a client a single exotic file format and hoped their machine could open it. Adopt the new format, keep the old one in your pocket. That instinct has never once let me down.

How to check it

1. Run the SEO Roadmap audit to confirm image format is flagged.
2. Run a page through PageSpeed Insights and look for “Serve images in next-gen formats”.
3. Open dev tools, reload a page, and check the Network tab to see whether images arrive as AVIF or WebP.
4. Confirm a fallback is served to browsers that do not support AVIF.

How to fix it in WordPress

Difficulty Level: EASY – This fix is straightforward and can typically be completed by anyone with basic WordPress knowledge.

Estimated Time: 15 min

Step 1: Let a plugin or CDN handle conversion

The clean path is an image-optimisation plugin or an image CDN that converts on the fly and serves AVIF or WebP with an automatic fallback based on the browser’s Accept header. This is far more reliable than hand-converting a library, and it covers future uploads too. WordPress itself has been expanding native AVIF handling, but a good plugin or CDN gives you the fallback logic without effort.

Step 2: Convert the existing library

Bulk-convert your current images through the plugin, keeping the originals so browsers without AVIF support still get a valid file. Do the conversion on a quiet window with a backup — it is processing-heavy on a large media library.

Step 3: Verify

1. Clear your cache and any CDN cache.
2. Reload a page and confirm in the Network tab that images arrive as AVIF, with a working fallback.
3. Re-run PageSpeed Insights and the SEO Roadmap audit to confirm the improvement.

Recommended Tools & Plugins

• Yoast SEO – Comprehensive SEO plugin with built-in checks
• Rank Math – Feature-rich SEO plugin with detailed analysis
• Google Search Console – Free tool to monitor your site’s search presence
• SEO Roadmap – Complete SEO audit and action plan tool

Common Mistakes to Avoid

• Serving AVIF with no fallback, breaking images for browsers that cannot render it.
• Chasing AVIF before fixing oversized images and layout shift, which matter more.
• Bulk-converting a large library on production during peak hours without a backup.
• Deleting the original files, leaving no valid fallback source.

Need More Help?

If you’re still having trouble, consider consulting a WordPress performance specialist, reviewing your image plugin or CDN documentation, and running a complete site audit with SEO Roadmap for a prioritized action plan.

This guide is part of the SEO Roadmap knowledge base – your complete resource for WordPress SEO optimization.