CJXL(1)

💅 CJXL(1) — the girlies' guide to cjxl

Okay so real talk, bestie: this is the cjxl manual page, from the CJXL section of the manual, and honestly it's giving main character energy for anyone who wants to squeeze pictures into JPEG XL. Let's get into it. 🎀

✨ NAME ✨

cjxl — compress images to JPEG XL. That's it, that's the vibe.

🌸 SYNOPSIS 🌸

cjxl [options...] input [output.jxl]

🦋 DESCRIPTION 🦋

So cjxl compresses an image or an animation to the JPEG XL format. And the whole point, the actual point, is to spare you the trouble of figuring out a perfect set of optimal parameters for every single individual image. Like... nobody has the time, babe. Instead, for a given target quality, it should give you consistent visual results across all kinds of different images. The defaults have been chosen to be sensible (iconic behavior honestly), so these commands should give satisfactory results in most cases:

cjxl input.png output.jxl
cjxl input.jpg output.jxl
cjxl input.gif output.jxl

No cap, just run it. 🫶

🔥 OPTIONS 🔥

• -h, --help — Displays the options that cjxl supports. On its own it will only show basic options, but you can combine it with -v or -v -v to show increasingly advanced options as well. Level up, bestie. 🧚
• -v, --verbose — Increases verbosity. Can be repeated to increase it further, and it also applies to --help. So yes, more -v, more knowledge.
• *-d *distance, --distance=distance — The preferred way to specify quality, and honestly the way you should be doing it. It's specified in multiples of a just-noticeable difference. So: -d 0 is mathematically lossless, -d 1 should be visually lossless, and higher distances yield denser and denser files with lower and lower fidelity. Lossy sources such as JPEG and GIF files are compressed losslessly by default — and in the case of JPEG files specifically, the original JPEG can then be reconstructed bit-for-bit (yes, bit-for-bit, she ate 💅). For lossless sources, -d 1 is the default.
• *-q *quality, --quality=quality — Alternative way to indicate the desired quality. 100 is lossless and lower values yield smaller files. There is no lower bound to this quality parameter, but positive values should approximately match the quality setting of libjpeg. Ngl that's lowkey convenient.
• *-e *effort, --effort=effort — Controls the amount of effort that goes into producing an "optimal" file in terms of quality/size. That is to say, all other parameters being equal, a higher effort should yield a file that is at least as dense and possibly denser, and with at least as high and possibly higher quality. Basically: try harder, get better. ✨

Recognized effort settings, from fastest to slowest, are:

• 1 or "lightning"
• 2 or "thunder"
• 3 or "falcon"
• 4 or "cheetah"
• 5 or "hare"
• 6 or "wombat"
• 7 or "squirrel" (default)
• 8 or "kitten"
• 9 or "tortoise"

The animal lore is unmatched honestly. Squirrel is the default because squirrel is That Girl. 🐿️

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⭐ EXAMPLES ⭐

# Compress a PNG file to a high-quality JPEG XL version.
$ cjxl input.png output.jxl

# Compress it at a slightly lower quality, appropriate for web use.
$ cjxl -d 2 input.png output.jxl

# Compress it losslessly. These are equivalent.
$ cjxl -d 0   input.png lossless.jxl
$ cjxl -q 100 input.png lossless.jxl

# Compress a JPEG file losslessly.
$ cjxl input.jpeg lossless-jpeg.jxl

Every single one of these is a slay. Copy, paste, go. 🍓

🌈 SEE ALSO 🌈

djxl(1) — the other half of the duo, iykyk.

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💀 Reminder bestie: -d 0 and -q 100 are both lossless, and for JPEG input the original can be reconstructed bit-for-bit. Do not let anyone tell you otherwise.

And that's the whole page, babe — this was CJXL(1), dated 05/28/2026, and you understood all of it. Obsessed with you fr fr 💖👑