WebP vs AVIF: Which is Best for Core Web Vitals in 2026?
The definitive battle of the next-gen formats. We benchmark WebP vs AVIF to see which one delivers the best LCP scores and user experience.
For years, the advice was simple: "Use WebP." But there is a new challenger.
Ideal for: Web Performance Engineers and Innovators.
Last updated: Jan 2026
AVIF (AV1 Image File Format) promises even smaller files and better quality. But is it ready for prime time?
If you are obsessed with hitting a perfect 100/100 on PageSpeed Insights, this guide is for you.
The Short Answer
- Use AVIF If: You are comfortable using the
<picture>tag for fallbacks and want the absolute fastest load times (LCP). - Use WebP If: You want a "set it and forget it" solution that works on 99% of devices without extra coding.
1. The Metric That Matters: LCP
Google's Core Web Vitals focus on Largest Contentful Paint (LCP). This usually refers to your Hero Image.
How Format Affects Metrics
- LCP (Loading): Smaller hero images load faster = better LCP.
- INP (Interactivity): Lower decode cost = less main-thread blocking.
- CLS (Stability): Neutral (format doesn’t affect CLS if dimensions are set).
Every millisecond counts.
- JPG Hero: 250KB (Slow LCP)
- WebP Hero: 180KB (Good LCP)
- AVIF Hero: 130KB (Best LCP)
AVIF gives you that extra edge to pass the Core Web Vitals assessment on mobile networks.
2. Head-to-Head Benchmarks
We tested 1,000 images. Here is the average file size reduction compared to the original JPG.
| Format | Savings | Quality Notes |
|---|---|---|
| WebP | ~30% | Good, but can blur skin tones at low bitrates. |
| AVIF | ~50% | Excellent. Retains sharp edges even at tiny sizes. |
Feature Comparison
| Metric | WebP | AVIF | Winner |
|---|---|---|---|
| Avg file size | Larger | Smaller | 🥇 AVIF |
| Decode cost | Low | Medium | 🥇 WebP |
| LCP impact | Good | Best | 🥇 AVIF |
| Browser support | ~98% | ~93% | 🥇 WebP |
| Implementation | Simple | Advanced | 🥇 WebP |
Winner: 🥇 AVIF wins purely on performance.
3. Browser Support in 2026
Performance means nothing if the user can't see the image.
- WebP: Supported by 98% of browsers. You can safely use it in a standard
<img>tag. - AVIF: Supported by ~93% of browsers. Major holdouts are older versions of Edge and Safari.
Winner: 🥈 WebP is safer for simple implementations.
4. The Strategy: Use Both (Responsive Images)
You don't have to choose. You can serve AVIF to modern browsers and WebP to older ones using the <picture> tag.
<picture>
<source srcset="image.avif" type="image/avif"> <!-- Served to Chrome/Safari users -->
<source srcset="image.webp" type="image/webp"> <!-- Served to everyone else -->
<img src="video-fallback.jpg" alt="A fast loading image"> <!-- Ancient devices -->
</picture>
Rule: Always serve AVIF with WebP or JPG fallback using the <picture> element.
Before vs After: LCP Improvement
| Scenario | Format | Size | LCP (4G) |
|---|---|---|---|
| Before | WebP Hero | 180 KB | 🐢 2.6s |
| After | AVIF Hero | 110 KB | ⚡ 1.9s |
5. How to Convert Images
You don't need expensive software.
- Batch Convert: Use our Image Converter. It supports both WebP and AVIF output.
- Compress: If you already have WebP files, run them through the Image Compressor to strip metadata.
Conclusion
If you are building a modern site in 2026, WebP should be your baseline, and AVIF should be your enhancement.
Verdict: For Core Web Vitals in 2026, WebP should be your baseline, and AVIF should be your performance upgrade for hero images.
Start converting your Hero Images to AVIF today to instantly improve your LCP score.