JP2 to JXL Converter
Convert JP2 to JXL in your browser. JP2 files usually come from libraries and digital archives, medical (DICOM) and satellite imaging, and digital cinema packages; JXL is the better fit for archiving and future-proof high quality storage. You get a JPEG XL encoded with libjxl compiled to WebAssembly, lossy at the quality you choose or lossless. Nothing is uploaded.
- Processed locally
- No upload, no wait
- No sign-up
- No watermark
Drop images here
or choose files · paste with Ctrl/⌘ V
JP2 expected · other image formats also work
How to use JP2 to JXL
- 1
Add your JP2 files: drop them here, choose them, or paste from the clipboard.
- 2
Set the quality.
- 3
Click Convert. Each file is decoded and encoded in a background thread on this device.
- 4
Download the .jxl files one at a time or together as a ZIP.
Why use Aback Images for jp2 to jxl
Where the JXL goes next
JXL opens in Safari 17+, macOS 14 and iOS 17, GIMP, Krita, ImageMagick and the libjxl tools.
JXL next to JP2
A lossy JXL usually comes out far smaller than the JP2, which stores wavelet coding: reversible 5/3 for lossless files, irreversible 9/7 for lossy ones.
The first lossy pass
The JP2 holds up to 16 bits per channel is common, more is possible with nothing discarded yet. This conversion is the first lossy encode these pixels see, and hard edges and flat colour show it first.
Processed on your device
Your images are decoded, edited and encoded inside this browser tab by Web Workers. Nothing is uploaded to a server.
JP2 vs JXL
What changes from JP2 to JXL
Encoding: the JP2 uses wavelet coding: reversible 5/3 for lossless files, irreversible 9/7 for lossy ones; JXL uses lossy VarDCT or lossless modular coding; existing JPEGs can be repacked without loss, and the download is a JPEG XL encoded with libjxl compiled to WebAssembly, lossy at the quality you choose or lossless.
Bit depth: up to 16 bits per channel is common, more is possible in the JP2; JXL allows 8 to 16 bits per channel, or floating point, and the JXL written here has 8 bits per channel. 12 and 16-bit JPEG 2000 files are reduced to 8 bits per channel.
Colour: sRGB, greyscale, YCC or a space described by an ICC profile in the JP2; JXL supports sRGB, Display P3, linear and other spaces described in the codestream, written here as 8-bit sRGB.
Transparency: the JP2 stores it as an extra component flagged as opacity; the JXL keeps it as an extra channel in the codestream.
Metadata: the JP2 can carry XML, ICC and resolution boxes; JXL can carry EXIF and XMP boxes in the container form, often stripped by encoders, but nothing is copied across.
About JP2
JPEG 2000 is a wavelet-based format that can be truly lossless or lossy, handles very high bit depths and huge images, and is used where long-term fidelity matters: archives, medicine, satellites and digital cinema.
A .jp2 file is a box structure: a 12-byte signature box, an 'ftyp' box, a 'jp2h' header box with the size and colour specification, then the 'jp2c' box holding the codestream, which begins with FF 4F FF 51.
JP2 files usually come from libraries and digital archives, medical (DICOM) and satellite imaging, and digital cinema packages.
About JXL
JPEG XL is a next-generation format designed to replace JPEG. It compresses better than JPEG and WebP, supports lossless, HDR and progressive decoding, and can losslessly repack existing JPEGs.
A JPEG XL file is either a bare codestream starting with FF 0A or an ISO base media container whose 'jxlc' box holds the codestream. A recompressed JPEG keeps a 'jbrd' box that lets the original JPEG bytes be rebuilt exactly.
When converting JP2 to JXL makes sense
JXL is the better choice for archiving and future-proof high quality storage, while JP2 suits archival masters and specialist imaging.
JXL strengths: Excellent lossy and lossless compression; Progressive decoding and HDR; Huge image sizes. Drawbacks to weigh: Browser support is limited (Safari only by default); Few apps can open it yet.
Limitations
- A JPEG 2000 file may be a lossless master or a lossy derivative; the file does not tell you which at a glance, so keep the original either way.
- Archival scans can be tens of thousands of pixels across, and decoding them needs a lot of memory on a phone.
- Chrome and Firefox do not display JPEG XL by default, so it is not yet a format for websites; it suits archives and apps that support it.
- Lossless JPEG XL is usually smaller than PNG for the same pixels.
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Frequently asked questions
Does converting JP2 to JXL lose quality?
JXL is lossy, so detail the eye barely notices is discarded to save space. 12 and 16-bit JPEG 2000 files are reduced to 8 bits per channel.
Is transparency kept in the JXL?
Yes. JP2 stores it as an extra component flagged as opacity, and the JXL is written with an alpha channel, so transparent areas stay transparent.
Which apps open JXL files?
Safari 17+, macOS 14 and iOS 17, GIMP, Krita, ImageMagick and the libjxl tools. It opens in Safari 17 and later; Chrome and Firefox do not display it by default.
Are my images uploaded anywhere?
No. Processing happens inside your browser with WebAssembly and Web Workers. The site only downloads the app code and codecs; your files never leave your device. You can confirm this with the live upload counter on the tool, or in your browser's network panel.
Can I process many files at once?
Yes. Drop a whole selection or folder. Files are processed in parallel on several worker threads, each result can be downloaded on its own, and everything can be saved as one ZIP.
Is it free? Is there a file limit or watermark?
It is free with no account, no watermark and no daily limit. The only limit is your device's memory: very large images (over roughly 100 megapixels) may be refused to keep the tab from crashing.