Why can't I open a JP2 file on Windows?

Windows' Photos app and Paint have never supported JPEG 2000, and Chrome, Edge and Firefox do not show it either. Safari did until 2024. This page decodes it in any browser.

Is converting JP2 to JPG lossless?

No: JPG compresses again and loses a little. For an exact copy, save as PNG, which keeps every pixel. If the JPEG 2000 holds more than 8 bits a channel, the 16-bit PNG keeps that too, for editing or archiving.

Was my JPEG 2000 compressed losslessly?

The details say which wavelet was used. The reversible 5/3 wavelet is what lossless JPEG 2000 uses (it can also be cut down to lossy); the irreversible 9/7 wavelet always loses something, usually invisibly.

Is my picture uploaded?

No. The file is decoded by this browser tab on your own device, and nothing is sent anywhere.

Stays on your computer How this works

Free JP2 viewer: open JPEG 2000 files and convert them to JPG or PNG

Open a .jp2, .j2k or .jpx picture on any computer or phone, see how it was made, and save it as JPG, PNG, WebP or a 16-bit PNG. The file is opened in your browser and is not uploaded.

Drop a .jp2 file here, or click to choose oneIt is opened by your browser, on this computer. Nothing is uploaded.

About the JP2 viewer

JPEG 2000 was meant to replace JPEG. It never did on the web, but it is everywhere else: scanned books and newspapers in libraries and archives (the Internet Archive's scans are JP2), digital cinema, satellite and aerial images, medical scans and some camera and scanner software. Windows, most browsers and phones do not open it, so a downloaded .jp2 often shows as an unknown file.

This page decodes it with OpenJPEG, the reference JPEG 2000 decoder, and reads the file's own description of itself: its colour space, bit depth, whether it was compressed losslessly, and its resolution. It is free to use, with no account and no upload limit, and it runs entirely in your browser: nothing is uploaded, and while the page stays open, a feature you have already used keeps working offline.

What you can do

See a greyscale or colour .jp2, .jpx or raw .j2k / .j2c codestream at full size, palettes included
Save it as JPG, PNG or WebP, or as a 16-bit PNG when the picture holds 12 or 16 bits a channel, as scans and medical images often do
See its size, colour space and bit depth, whether it used the lossless or the lossy wavelet, its resolution levels, quality layers and tiles

Pictures with a transparency channel, or in CMYK, are not decoded yet: the page says so and shows their details.

How to convert JP2 to JPG

Drop the .jp2 file on the box above, or click the box and choose it.
The picture appears with its details.
Click Save as JPG, or PNG to keep every detail.

Questions

Why can't I open a JP2 file on Windows?: Windows' Photos app and Paint have never supported JPEG 2000, and Chrome, Edge and Firefox do not show it either. Safari did until 2024. This page decodes it in any browser.
Is converting JP2 to JPG lossless?: No: JPG compresses again and loses a little. For an exact copy, save as PNG, which keeps every pixel. If the JPEG 2000 holds more than 8 bits a channel, the 16-bit PNG keeps that too, for editing or archiving.
Was my JPEG 2000 compressed losslessly?: The details say which wavelet was used. The reversible 5/3 wavelet is what lossless JPEG 2000 uses (it can also be cut down to lossy); the irreversible 9/7 wavelet always loses something, usually invisibly.
Is my picture uploaded?: No. The file is decoded by this browser tab on your own device, and nothing is sent anywhere.

Built by John McMillan, a senior full-stack engineer. Open to remote roles: hire me.

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