B3K File
What are B3K files and how to open them
Are you having problems opening a B3K file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your B3K files.
What is a B3K file?
A .B3K file is a BWTC32Key Encoded file.
BWTC32Key Encoded files store binary data that has first been compressed, then optionally encrypted, and finally converted into a text-friendly encoding. They are produced by the BWTC32Key tool, which uses the Burrows - Wheeler Transform with a range coder for compression, allows optional AES-256-CTR encryption under a password, and encodes the result into a Base32768 text form combining Unicode characters from selected planes.
The encoding makes the file suitable for transmission or storage environments that only accept text, while still retaining both compression and encryption features. If no password is set, the output is compressed but not encrypted; when a password is supplied, the encrypted content is embedded in the text. To recover the original data the BWTC32Key tool must reverse all steps: decode Base32768, decrypt with AES-256-CTR (if used), then decompress via the reverse of its BWT + range coder pipeline.
BWTC32Key Encoded files begin with a distinctive byte sequence signature: EF BB BF E4 B4 80 at the very start of the file.
How to open B3K files
Important: Different programs may use files with the B3K file extension for different purposes, so unless you are sure which format your B3K file is, you may need to try a few different programs.
We have not yet verified any programs for Windows that work with this specific file format. If you know one, please use the 'Suggest a program' link below. Thanks!
Last updated: August 22, 2026
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