MiniPx
PricingBlogAccount

JPEG XL, explained

The format that was meant to replace JPEG, where it actually stands, and what to encode to instead while you wait.

🖼️
Encode to AVIF instead →

MiniPx writes AVIF, WebP, JPEG and PNG. It does not write .jxl — no browser exposes a JXL encoder.

JPEG XL Converter — Free, Fast & Private

Start with the disclosure, because most pages ranking for this query bury it: MiniPx cannot produce a .jxl file. Encoding happens in your browser, and no browser exposes a JPEG XL encoder to web pages. Anything claiming a free in-browser JXL converter is either shipping a large WebAssembly encoder or uploading your image to a server. MiniPx does neither, so the honest answer is that this page explains the format rather than converting to it.

JPEG XL is a 2022 ISO standard from the JPEG committee, designed to replace JPEG, PNG, GIF and WebP with one format. At equal visual quality it typically lands 30-60% below JPEG. It supports lossless compression, alpha, animation, HDR, high bit depths and progressive decoding, and it decodes fast — noticeably faster than AVIF at large resolutions.

Its most interesting trick is lossless JPEG recompression. An existing JPEG can be transcoded into JXL, shedding roughly 20% of its bytes with zero quality change, and the original JPEG can be reconstructed bit-for-bit. No other modern format does that, which is why archives care about JXL more than websites do.

Decoding support is the sticking point. Safari has decoded JXL since version 17. Chromium removed its flag-gated support in 2023 and support has moved in fits and starts since; Firefox has kept its implementation behind a flag for years. Check caniuse.com before you commit — the state of play changes, and a page that hardcodes a version number goes stale within months. Note also that decoding is not encoding: even a browser that displays JXL will not let a web page write one.

So what should you ship today? AVIF gets you most of the size win with support in every current browser engine. WebP is the safe universal choice. Serve either through a picture element with a JPEG fallback and you have captured the practical gain that JXL promises, using formats MiniPx can actually encode.

How it works

  1. Skip JXL for delivery, for now: No browser lets a web page encode JPEG XL, and decode support is inconsistent. That rules it out as a delivery format for most sites today.
  2. Encode to AVIF for the biggest win: Open MiniPx, pick AVIF as the output format, and use the Smart preset. AVIF typically lands 30-50% below WebP at matching quality and decodes everywhere current.
  3. Keep WebP or JPEG as the fallback: Serve AVIF first and WebP or JPEG second inside a picture element. Every browser gets something it can render.
  4. Re-check support before switching: If you archive rather than publish, JXL lossless JPEG recompression is worth watching. Verify current decode support on caniuse.com rather than trusting a version number in an article.

Frequently asked questions

Can MiniPx convert my images to JPEG XL?
No. MiniPx encodes in your browser, and browsers do not expose a JPEG XL encoder to web pages. MiniPx outputs AVIF, WebP, JPEG and PNG. Any free tool that claims in-browser JXL conversion is either downloading a heavy WebAssembly encoder or sending your image to a server.
What is JPEG XL?
A 2022 ISO image format from the JPEG committee, intended to replace JPEG, PNG, GIF and WebP with one codec. It compresses roughly 30-60% better than JPEG at matching quality and adds alpha, animation, HDR, high bit depth and progressive decoding.
Which browsers support JPEG XL?
Decode support is patchy and has changed direction more than once. Safari has decoded JXL since version 17; Chromium removed its flag-gated support in 2023; Firefox has kept its implementation behind a flag. Check caniuse.com for the current position rather than trusting a stated version number. Decoding is not encoding — no browser lets a page write a .jxl file.
Is JPEG XL better than AVIF?
They are close on compression, with AVIF often ahead at very small sizes and JXL ahead on large images. JXL decodes faster, supports progressive loading, and can losslessly recompress an existing JPEG. AVIF has the decisive practical advantage today: it works everywhere, and MiniPx can encode it.
Is JPEG XL better than WebP?
On compression, yes — typically 20-35% smaller at matching quality, with higher bit depths and better colour handling. On availability, no. WebP renders in every browser in use and is a format you can actually produce.
What should I use instead right now?
AVIF for the largest size reduction, WebP as the compatibility fallback, both served from a picture element with a JPEG last resort. That captures nearly all of the benefit JXL promises using formats you can encode today.
Will MiniPx add JXL output later?
Only if browsers ship an encoder a web page can call, or if a WebAssembly encoder becomes small enough to load without punishing mobile users. Shipping a multi-megabyte download for a format most browsers will not display is not a trade we would make quietly.

All Image Tools

AI Tools

Pro Tools

Compress

Convert

Resize

Compress to Size

Compress for Platform

Tools & Utilities

By Device

Compare

Solutions by use case

For Developers & Web

For Sellers & Ecommerce

For Job Applicants & Govt Forms

For Creators & Social

For Work & Documents