How to Batch Convert Images to JPEG XL (.jxl) on a Mac

Published by @SoNiceInfo at 9/21/2026

The easiest way to batch convert JPG, PNG, and HEIC images to JPEG XL (.jxl) on a Mac is a GUI app such as Image Tool+: drag and drop your images or folders, pick JPEG XL as the output format, and your images never leave your Mac. If you're comfortable in the terminal, the official encoder cjxl, installed via Homebrew, works too. Note that the sips command built into macOS can read JPEG XL but cannot write it, so the built-in tools alone can't create a .jxl file (details below).

The two methods compared

JPEG XL is an image format designed as the successor to JPEG. It supports both lossy and lossless compression, high bit depth, HDR and wide color gamut, and progressive decoding. There are effectively two ways to create .jxl files offline on a Mac: a GUI app and the cjxl command.

RecommendedMethod 1: Drag and drop with Image Tool+

Image Tool+, a batch image converter for Mac, is a Mac-only app I develop. It reads HEIC, PNG, JPG, GIF, TIFF, PSD, PDF, and more, and exports to 10 formats including JPEG XL. Using it takes three steps: drag images or a folder into the window, pick an output format, and hit Start.

Along with the conversion, it handles resizing, renaming, watermarking, metadata editing, and background removal in the same pass, and it preserves HDR and wide-gamut color on export. Everything is processed on your Mac, with no need to upload images anywhere. It's a one-time purchase with no subscription.

Note that the sibling apps WebP Converter. and AVIF Converter. specialize in WebP and AVIF respectively and do not export JPEG XL. For JPEG XL, Image Tool+ is the one to use.

For terminal usersMethod 2: Install cjxl via Homebrew

cjxl is the official encoder that ships with libjxl, the JPEG XL reference implementation. It's easy to script, and it can do the lossless JPEG recompression described below. With Homebrew installed, one command gets it. The decoder djxl comes along with it.

brew install jpeg-xl

When the input is a JPEG, cjxl performs a lossless transcode by default. The image quality doesn't change at all; only the file gets smaller.

cjxl input.jpg output.jxl

A .jxl made this way can be turned back into the original JPEG with djxl. On my Mac I confirmed with cmp that the restored JPEG is bit-for-bit identical to the original file.

djxl output.jxl restored.jpg

For lossy conversion from PNG and similar sources, set the quality with -d (distance). -d 1 is visually near-lossless, and larger values give smaller files.

cjxl input.png output.jxl -d 1

For logos, screenshots, and other images you don't want degraded, use -d 0 for lossless compression.

cjxl input.png output.jxl -d 0

• -d — quality (distance). 0 is lossless and 1 is visually near-lossless; larger values mean smaller, rougher output.
• -e — encoding effort. The default is 7; higher values take longer and make files slightly smaller.

To convert every JPG in a folder, use a shell for loop. The originals stay in place and files with the same name and a .jxl extension are created.

for f in *.jpg; do cjxl "$f" "${f%.*}.jxl"; done

Note that cjxl cannot read HEIC directly. To convert iPhone HEIC photos, first convert them to JPEG or PNG with sips, or use Method 1, which reads HEIC as is.

macOS's built-in sips can't write JPEG XL

Can't the built-in tools do it? At the time of writing, the answer is: they can display and read JPEG XL, but not write it. macOS 14 Sonoma and later can display JPEG XL, so Quick Look in Finder and Preview.app open .jxl files. You can check which formats the built-in conversion command sips supports with this command.

sips --formats | grep -i jxl

On my Mac (macOS 27) it prints public.jpeg-xl jxl, but without the Writable marker that the JPEG and PNG rows have. Running sips -s format jxl produced no file. The other direction, JPEG XL to JPEG, does work with sips.

sips -s format jpeg input.jxl --out output.jpg

Measured: how much smaller do files get?

Here is what happened when I converted a single 1600×1064 photo with cjxl. It's one example only; savings vary with the image content and settings.

Test environment: macOS 27, cjxl v0.12.0.

The first row is the one to notice. Photos you already have as JPEGs become about a fifth smaller without changing a single bit of image quality, and you can get the original JPEG back whenever you need it.

Browser and app support

JPEG XL support is still changing. The following is as of the time of writing and partly based on secondary sources; check caniuse.com/jpegxl for the current status.

• Safari — Safari 17 and later displays JPEG XL out of the box.
• Chrome — Chrome 145 (February 2026) brought the decoder back, but it's off by default and must be enabled with a flag.
• Firefox — Firefox 152 (June 2026) includes a decoder, also off by default.
• macOS — macOS 14 Sonoma and later displays .jxl in Finder and Preview.app.

Chrome and Firefox both plan to turn it on by default, but for now, serving JPEG XL on a website requires a <picture> fallback. The browser loads the first format it supports, from top to bottom.

<picture>
  <source type="image/jxl" srcset="/images/hero.jxl" />
  <source type="image/avif" srcset="/images/hero.avif" />
  <source type="image/webp" srcset="/images/hero.webp" />
  <img src="/images/hero.jpg" alt="..." width="1600" height="1064" />
</picture>

Where JPEG XL shines today is archiving photos rather than delivery. It stores JPEGs about 20% smaller with no loss and can restore the original; it handles high bit depth, HDR, and wide color gamut; and it supports progressive decoding. For photographers who want to keep their shoots for the long term, those are all practical benefits.

Which method fits you

• Photographers — To store an existing JPEG library smaller without touching image quality, use the lossless transcode in cjxl; you can restore the original JPEGs at any time. To export masters in JPEG XL with HDR and wide gamut preserved, or to resize and rename in the same pass, Image Tool+ is the better fit.
• Web creators and bloggers — AVIF and WebP are still the delivery baseline. If you use JPEG XL, add it as the first source in a <picture> element. Image Tool+ can export JPEG XL, AVIF, and WebP in a single pass. For choosing a format, see WebP vs AVIF.
• Engineers — For scripts and build pipelines, use cjxl. -d and -e give you fine control over quality and speed.

FAQ

Summary

To batch convert images to JPEG XL on a Mac, start with the GUI app Image Tool+: drag and drop your images, HEIC included, and resize or rename them in the same pass. If you work in the terminal, or want to store JPEGs smaller with no loss, choose cjxl. The built-in sips command can't write JPEG XL. Either way, your images never leave your Mac.

Related guides

• How to batch convert images to AVIF on a Mac
• How to batch convert PNG and JPG to WebP on a Mac
• How to batch convert HEIC to JPG, PNG, or WebP on a Mac
• WebP vs AVIF: differences and when to use each