The Problem With Image Formats
You upload a JPEG. It looks great. But your site loads slowly.
You switch to WebP. Faster. But is quality good enough?
You hear about AVIF. Smaller files. But do browsers support it?
Choosing the right image format is confusing. Get it wrong, and your SEO suffers. Get it right, and your site flies.
This guide compares the three major formats. No fluff. Just what you need to know.
Quick Comparison
| Format | File Size | Quality | Browser Support | Best For |
|---|---|---|---|---|
| JPEG | Large | Good | 100% | Photos where quality matters more than speed |
| WebP | Medium | Very Good | 97% | Most websites. Best balance of size and quality |
| AVIF | Small | Excellent | 90% | Cutting-edge sites. Smallest file sizes |
JPEG
The old reliable.
JPEG has been around since 1992. Every browser supports it. Every device opens it.
Pros:
Universal browser support (100%)
Good quality for photographs
Everyone knows how to use it
Cons:
Largest file size of the three
No transparency (no alpha channel)
Older compression technology
Best for: Photographs where quality matters more than file size, or when you need guaranteed compatibility with very old browsers.
WebP
The modern standard.
Google created WebP in 2010. It took years to gain support. Now it is everywhere.
Pros:
25-35% smaller than JPEG at same quality
Supports transparency and animation
Supported by 97% of browsers (all modern ones)
Cons:
Slightly less quality than JPEG at very high compression
Older browsers (Internet Explorer) do not support it
Best for: Most websites. The best balance of file size, quality, and browser support.
AVIF
The new competitor.
AVIF emerged in 2020. It is based on the AV1 video codec. It promises the smallest files yet.
Pros:
50% smaller than JPEG at same quality
30% smaller than WebP
Excellent quality even at high compression
Supports HDR and wide color gamut
Cons:
Only 90% browser support (older devices may not load it)
Slower to encode (takes more processing power)
Still gaining adoption
Best for: Cutting-edge websites willing to accept slightly lower browser support for maximum speed.
Which Format Wins for SEO?
For speed (Core Web Vitals): AVIF wins. Smallest files. Fastest loading.
For compatibility: JPEG wins. Every browser. Every time.
For balance: WebP wins. Great size. Great support. Great quality.
Our recommendation: Use WebP as your default. Use AVIF for critical images where every kilobyte matters. Use JPEG only for backwards compatibility.
How WriteAlt Handles Image Formats
WriteAlt supports every format you need.
Upload anything:
JPG, PNG, WebP, AVIF, SVG, GIF, BMP, HEIC
No extra cost for advanced formats:
AVIF and WebP cost the same as JPEG. No hidden fees. No upcharges.
Export your way:
Download images in their original format. Or choose WebP for optimized web delivery. Your images. Your choice.
Direct to WordPress or Shopify:
Export alt text and images directly to your CMS. Images arrive ready to use. No quality loss. No manual conversion.
Independent downloads:
Download ZIP files with all your images and alt text together. Keep your own backups. Move to any platform. You stay in control.
Quality Loss? Not With WriteAlt
Some tools compress your images without telling you. Quality suffers. Your product photos look worse.
WriteAlt does not do that.
When you export your images, they retain original quality. No compression. No resizing. No surprises.
You choose the format. You keep the quality.
The Bottom Line
| Your Situation | Best Format |
|---|---|
| Maximum browser compatibility | JPEG |
| Best balance of size and support | WebP |
| Smallest files possible | AVIF |
| You use WriteAlt | All three. You choose. |
WriteAlt supports every format. No extra cost. No quality loss. Export to WordPress, Shopify, or download ZIP files with original images.
Ready to Optimize Your Images?
WriteAlt generates alt text for any image format you upload. WebP, AVIF, JPEG — all work the same. One credit per image. No hidden fees.
Try 25 images free. No credit card required.
