Images are usually the heaviest assets on a web page, so the format you choose directly shapes load time, Core Web Vitals and ultimately your Google ranking. According to web.dev, the Largest Contentful Paint (LCP) element is an image on about 73% of mobile pages — meaning your image strategy *is* your performance strategy for most sites. In 2026, the answer for the majority of sites is clear.
Why format choice affects your ranking
Core Web Vitals have been a confirmed Google ranking signal since 2021, and a good LCP is 2.5 seconds or less. They act as a tiebreaker: a page with excellent content but poor vitals can lose to a slightly less authoritative but faster competitor. Since only about 62% of mobile pages pass LCP, optimising images is one of the highest-leverage SEO moves available — and modern formats can cut image weight by a third (WebP) to a half (AVIF).
WebP vs AVIF: which to use
| Format | Size vs JPEG | Browser support | Use when |
|---|---|---|---|
| WebP | 25–34% smaller | ~97% | Your reliable default for all images |
| AVIF | up to ~50% smaller | ~94% | Max performance, with a WebP fallback |
| JPG | baseline | Universal | Legacy fallback / form uploads |
| PNG | larger (lossless) | Universal | Logos, icons, transparency |
Default to WebP — convert your photos with our Image to WebP tool for a free 25–34% size cut with no visible quality loss. If you want to push further, serve AVIF as the primary source with WebP as the fallback in a `<picture>` element so modern browsers get the smallest file and everyone else still sees an image.
Format alone isn't enough
Always compress images to a sensible size before publishing — most web photos look great at 100–200KB. Oversized images are the single most common cause of slow pages. And don't ship a 4000px-wide photo into an 800px-wide column: resize to roughly the largest size it will actually display. Use Reduce Image Size and Compress Image to 100KB to do both.
A simple four-step workflow
- Resize to the maximum display width you need (e.g. 1600px for full-width heroes).
- Convert to WebP (or AVIF with a WebP fallback).
- Compress to a target size — 100–200KB for most photos.
- Add descriptive alt text and set width/height to prevent layout shift (CLS).
Frequently asked questions
- What is the best image format for a website in 2026?
- WebP for almost everything — it's ~25–34% smaller than JPG with ~97% browser support. Use AVIF (even smaller) with a WebP fallback when you want maximum performance, and PNG for logos or transparency.
- Do images really affect SEO?
- Yes. The LCP element is an image on ~73% of mobile pages, and Core Web Vitals are a confirmed ranking tiebreaker. Lighter images mean faster LCP, which can lift rankings on competitive queries.
- Should I switch from WebP to AVIF?
- Not entirely. Keep WebP as the dependable default and add AVIF as a primary <picture> source with a WebP fallback — AVIF is smaller but reaches a few percent fewer users.