CBT (Comic Book TAR) file format

.cbt · package (TAR variant) · introduced 2003 by Comic reader community

What is a CBT (Comic Book TAR) file?

CBT is a TAR-based comic book archive. Because TAR does not compress, CBT files are no smaller than the sum of their page images, but they open extremely quickly on slow CPUs. Rare in the wild.

Most readers reach this page after double-clicking a .cbt file and finding their operating system unsure what to do with it. The good news: CBT (Comic Book TAR) is a well-understood format with mature tooling on every major platform. It is supported in one click by mainstream archivers on Windows, macOS, and Linux.

How to extract a CBT (Comic Book TAR) file

Opening a .cbt file is straightforward on every modern operating system. The exact steps depend on which platform you are on:

On Windows

Locate the .cbt file in File Explorer.
Right-click the file. If you have 7-Zip installed, choose 7-Zip → Extract Here. On Windows 11 the built-in extractor handles ZIP, 7z, RAR and several other formats directly through Extract All…
If prompted, pick a destination folder and click Extract.
The extracted files appear in a folder next to the original archive.

On macOS

Find the .cbt file in Finder.
Install The Unarchiver from the Mac App Store, or Keka for both creating and extracting.
Right-click the file → Open With → The Unarchiver (or just double-click after Unarchiver is set as the default).
The extracted folder appears next to the archive.

On Linux

Use your file manager: right-click the archive → Extract Here (file-roller on GNOME, Ark on KDE).

On the command line, run one of:

7z x archive.cbt    # works for almost any format

The files appear in the current directory.

How to create a CBT (Comic Book TAR) file

To pack files into a .cbt archive, you typically need an archiver that supports writing this format. Not every tool can create every format — for example, only WinRAR can create real RAR files. The sidebar lists the software known to read and write CBT (Comic Book TAR).

On the command line, the canonical create command is:

# Use 7-Zip, PeaZip, or the format's reference tool to create .cbt files.

If you regularly create archives at scale, a dedicated archive automation suite can wrap this command in scheduled jobs, integrity checks, and offsite replication.

Strengths

Trivial to open
No CPU overhead

Weaknesses and limitations

No compression
Niche

Typical use cases

Embedded comic readers
High-speed page access on slow hardware

Technical details

CBT (Comic Book TAR) uses the TAR (no compression) algorithm and is identified on disk by the magic byte sequence 75 73 74 61 72. The standard MIME type is application/x-cbt. The format is an open specification and is free for any use.

Frequently asked questions

Is CBT (Comic Book TAR) safe to open?

Archive files are containers — they are only as safe as what they contain. A .cbt from a trusted source is fine; one received from a stranger can hold malicious executables, scripts, or files engineered to exploit bugs in your archiver. Always keep your archiver updated, and never run unknown executables that come out of an archive. A safe workflow is to extract into a sandbox and scan the contents before opening anything.

What is the maximum file size?

Modern implementations support archives in the multi-terabyte range. The practical limit is your filesystem (FAT32 caps at 4 GB; ext4, NTFS, APFS, and exFAT all comfortably handle multi-TB files).

Can I password-protect a CBT (Comic Book TAR)?

Some archivers can wrap CBT (Comic Book TAR) files in an encrypted container, but the format itself does not always include built-in encryption. Check your archiver's documentation.

How does CBT (Comic Book TAR) compare to other formats?

See our format comparison pages such as ZIP vs 7z, ZIP vs RAR, and tar.gz vs tar.xz for side-by-side feature tables.