How to use it
- Drop in JPEG 2000 files.
- Each is decoded with OpenJPEG in your browser.
- Download the JPGs.
Where JPEG 2000 turns up
JPEG 2000 was published in 2000 as a more advanced successor to JPG, using wavelet compression instead of 8 × 8 blocks. It never took off on the web, but it became established in specialist fields: digitised collections at national libraries and archives, satellite and aerial imagery, medical imaging, and digital cinema, where film projection packages use it frame by frame. If you have downloaded a scan from a library or a map tile from a government service, it may well be .jp2.
Why ordinary apps struggle
Support in everyday software is thin and has shrunk over time, and browsers generally do not display it. This converter decodes the file with OpenJPEG, the reference open-source implementation, compiled to WebAssembly.
Very large images
Archive scans can be enormous, sometimes tens of thousands of pixels across. Computers handle these, though slowly; phones may scale them to fit memory and will tell you when they do.
JPEG 2000 and JPG compared
| JPEG 2000 | JPG | |
|---|---|---|
| First released | 2000 | 1992 |
| Compression | Lossy or lossless (wavelets) | Lossy |
| Transparency | Yes | No |
| Animation or pages | Tiles and resolution levels | No |
| Best for | Archives, mapping, medical and cinema | Photos for sharing, email and print |
| Support | Specialist software; little browser support | Universal |
Questions people ask
What is a JP2 file?
A JPEG 2000 image, common in archives, mapping and medical imaging.
Which extensions are supported?
.jp2, .j2k, .j2c and .jpc; many .jpf and .jpx files work too.
Is JPEG 2000 better than JPG?
Technically it offers better quality at the same size and a lossless mode, but support is far narrower.