What is a .j2k file?
A .j2k file is a JPEG-2000 codestream. Its registered MIME type is image/x-jp2-codestream, which places it in the image family of formats.
J2K is a binary format: the contents are not readable text, so opening it in a text editor shows scrambled characters.
Files of this type usually begin with the bytes FF 4F FF 51. That signature is how programs recognise the format even when the extension is wrong or missing.
The same format is also saved with the extensions .j2c, .jpc.
J2K file format details
| Extension | .j2k |
|---|---|
| Format | JPEG-2000 codestream |
| MIME type | image/x-jp2-codestream |
| Category | Image |
| Text or binary | Binary |
| File signature | FF 4F FF 51 |
| Registered with IANA | No |
| Other extensions | .j2c, .jpc |
How to open J2K files
| Windows | The Photos app handles common image formats; for this one you may need an image editor. GIMP is free and opens many formats. |
|---|---|
| Mac | Preview opens most image formats. If it cannot, a dedicated image editor usually can. |
| iPhone and iPad | Photos and the Files app show common image types. Less common ones may need an app, or conversion to JPG or PNG. |
| Android | Google Photos and gallery apps show common images. Other formats may need a viewer app. |
Can you convert a .j2k file?
TapToConvert does not convert J2K files yet. If you can export the file from its program as a common image format, the image converter can turn it into anything else.
J2K file FAQ
What is a .j2k file?
A .j2k file is a JPEG-2000 codestream, with the MIME type image/x-jp2-codestream.
How do I open a .j2k file?
With the program that created it. The viewer on this page shows what is inside without installing anything.
Is a .j2k file safe to open?
J2K files hold data rather than programs, but any file from an unknown source can be crafted to exploit the software that opens it. Keep that software up to date. The viewer on this page only reads the bytes and never runs anything.
What is the MIME type of .j2k?
image/x-jp2-codestream. Web servers send this type so browsers know how to handle the file.
Is J2K a text or binary format?
Binary. Its contents are not readable as text.
File type facts come from the IANA media type registry, the mime-db project and the freedesktop.org shared MIME database.