WebP vs. AVIF: Which Image Format Is Best for SEO in 2026?

The format war between WebP and AVIF has been running since AVIF landed in Chrome 85 in 2020. Six years later, both are widely supported — but the choice is more nuanced than "AVIF is newer, therefore better." For SEO specifically, the metric that matters is LCP (Largest Contentful Paint) — how quickly the largest image on the page becomes visible. That's determined by file size, decode speed, and CDN support, not just compression ratio.

Compression Ratio: AVIF Wins — But Not Always

At equivalent visual quality (measured by SSIM), AVIF typically achieves 20–40% smaller files than WebP for photographic content. This advantage narrows for:

• ●Images smaller than 200×200px — AVIF container overhead reduces the advantage
• ●Line art, screenshots, and text-heavy images — where WebP or PNG is often more efficient
• ●Images already compressed to JPEG at quality 60 or below — further AVIF compression adds artefacts without meaningful savings

Browser Support in 2026

• ●WebP: 97.8% global support — effectively universal, including all modern browsers and Safari 14+
• ●AVIF: 93.2% — Chrome, Firefox, Safari 16+, Edge 121+. Missing: iOS 15 Safari and some older Edge versions

<picture>
  <source srcset="hero.avif" type="image/avif">
  <source srcset="hero.webp" type="image/webp">
  <img src="hero.jpg" alt="Hero image" width="1200" height="630" loading="lazy">
</picture>

Encoding Speed: WebP Wins Significantly

• ●WebP (libwebp): 50–200ms for a 2MP image at quality 80
• ●AVIF (libaom): 2,000–15,000ms for the same image at equivalent quality
• ●AVIF (SVT-AV1): 300–800ms — the best speed/quality trade-off for production pipelines

For build-time optimisation (static sites, CI pipelines), AVIF is viable with aggressive caching. For runtime processing (user uploads, dynamic resizing), WebP is far more practical.

The SEO Verdict for 2026

For most production websites: serve both using the <picture> element. AVIF as primary for photographic content, WebP as the fallback.

If you can only pick one: use WebP. The 6.8% of users without AVIF support is not worth the broken-image risk, and WebP compression is good enough to pass Core Web Vitals when sized correctly. Start converting your images to WebP today.