Choosing the right image format is the single biggest lever for web performance. Pick wrong and a 90 KB photo becomes a 600 KB PNG. This guide covers JPEG, PNG, WebP, AVIF, and JPEG XL — and tells you exactly which to use when.
The five formats at a glance
- JPEG — Lossy, no transparency, universal. Best for photographs where compatibility beats size.
- PNG — Lossless, alpha transparency. Best for screenshots, icons, and graphics needing crisp edges.
- WebP — Lossy or lossless, alpha, animation. The best all-rounder in 2026.
- AVIF — Lossy, alpha, HDR, smallest files. Best for hero photos when you can cache the encode.
- JPEG XL (JXL) — Lossy or lossless, can reconstruct original JPEGs losslessly. The forward-looking choice.
Match the format to the content
Photographs
Use AVIF first (smallest), WebP as a universal fallback, and a JPEG as the final fallback. A <picture> tag with all three covers every browser.
Screenshots with text
Text stays crisp with PNG, but a high-quality WebP (q 90+) is nearly as sharp at half the size. Avoid JPEG — it smears text.
Icons & UI graphics with transparency
PNG is reliable; WebP lossless with alpha is a great modern alternative. For tiny icons, prefer SVG altogether.
Animations
Prefer WebP or AVIF animations over GIF, which is wildly inefficient.
Quality settings that just work
For lossy formats, these are safe defaults that look good and stay small:
- AVIF: quality 50 — visually clean, aggressively small.
- WebP: quality 75 — the sweet spot for most photos.
- JPEG: quality 75 — indistinguishable from source for most photos.
- JXL: quality 75.
- PNG: lossless — use OxiPNG optimization.
These are exactly Kix Image Tools's built-in defaults, so you can start there and nudge the slider if needed.
Serving strategy
Use the <picture> element with multiple <source> tags so the browser picks the best format it supports. Always set width and height to prevent layout shift, and add loading="lazy" for below-the-fold images.
Summary
There's no single "best format" — match the format to the content. Photos → AVIF/WebP. Screenshots → PNG or lossless WebP. Icons → SVG first, PNG/lossless WebP second. Need to act on all of this now? Convert your images in Kix Image Tools.