.CBT File

The CBT file extension is used for comics books archives. The *.cbt files are basically renamed TAR archives and can be decompressed with any TAR file utility. 

Compressed set of jpg, png, or static gif images. Pages are automatically ordered and can be presented one or two at a time. File format used for displaying comic books or other collections of pages.

This file format is typically used for comics.

A cbt file extension is used for a popular comic ebook format. CBR is basically a cbt file that contains several images (usually JPGs) that can opened in comic books viewer as a sequence of screens.

How to open:

You can use CDisplay Comic Reader or similar software, capable to read *.cbt files.

How to convert:

A *.cbt file is basically TAR archive file with renamed file extension TAR on CBT file extension. So you can simply extract the files and repack them to another archive format or access the images inside.