Convert PNG to JXL

JXL is the one format that beats PNG at lossless

Most modern formats are lossy, which makes them a poor choice for archiving and for anything you intend to edit again. JPEG XL is the exception: it offers a genuine lossless mode, and in that mode it typically produces a smaller file than PNG for the same pixels. That is a narrow but real advantage, and it is the only situation where converting a PNG to JXL is a clear improvement rather than a trade.

NoteThese are indicative. Very simple images with few colours can be nearly the same size in PNG and lossless JXL.

And the other mode nobody expects

Beyond lossless storage, JPEG XL has a feature no other format offers: it can recompress an existing JPG losslessly and recover the original file byte for byte. That makes it genuinely useful for archiving a large existing JPG collection, because the files can be made substantially smaller with nothing lost. It does not help with a PNG source, because there was no original JPG bitstream to preserve. So the two modes serve different purposes and only one of them applies here.

• Lossless mode: stores the pixels exactly, usually smaller than PNG.
• Reversible JPG recompression: recovers an original JPG perfectly. Needs a JPG source.
• A PNG source has no original JPG bitstream, so the reversible mode does not apply.
• For PNG sources, use the ordinary lossless mode.

The catch: almost nothing opens JXL

This is the deciding factor. Browser support for JPEG XL is incomplete, with some browsers behind a flag, and it is not supported by most design tools, publishing platforms, or operating system previews. A file in this format is effectively locked unless the recipient installs something. So converting a PNG to JXL is right for an archive you control and wrong for a file you intend to send, upload, or use on a website.

• Archive you control: JXL is a good lossless choice and often smaller than PNG.
• Anything you will upload to a CMS: keep the PNG, most systems reject JXL.
• Email or sharing: JXL will not open for the recipient.
• The web: JXL is not a practical web format despite its qualities.
• Keep a PNG alongside if the file may need to leave your archive.

MDN: image file type and format guide

When to keep the PNG instead

In most everyday situations the PNG is the better file and this conversion is not worth doing. If the image is going to a website, PNG and WebP both work and JXL does not. If it is going to a print supplier, they will want TIFF or PNG. If it is going into a design tool, the tool will not open it. The honest summary is that JXL is a specialised archival format, and the specialisation is the point rather than a limitation to work around.

• Web delivery: WebP or AVIF, not JXL.
• Print: TIFF or PNG, not JXL.
• Editing in a design tool: PNG, because the tool will not open JXL.
• Long term archive you control: JXL is a good lossless option.