CKIT File

What are CKIT files and how to open them

Are you having problems opening a CKIT 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 CKIT files.

What is a CKIT file?

A .CKIT file is a Compression KIT Compressed C64 Disk file.

Compression KIT Compressed C64 Disk files store complete logical images of Commodore 64 disks that have been compressed into a single archive. Created by Mad Man Software's Compression Kit, these files are used for backing up, compressing, and distributing whole-disk data from 1541, 1571, 1581 floppy drives, RAM devices (RAMDrive, RAMLink), and CMD hard- or floppy-based storage. The format enables accurate restoration of a disk's file structure and metadata after compression.

The Compression Kit utility writes these compressed disk images. The workflow typically involves selecting a disk or storage partition as the source, compressing its contents - including all files and directory metadata - into one archive file, then later using the included Decomper tool to expand ("dearchive") that image back into a usable disk format. Features include the ability to compress sets of PRG, SEQ, or USR files individually, or to capture an entire device or disk into the archive. For enhanced speed and capacity, operations may use extra RAM or RAMLink/CMD partitions, and on a C128 machine the utility can switch to a 2-MHz mode during compression (though actual disk operations still run at standard speed).

The format's internal identifier appears in the file header: the first bytes are the ASCII sequence "MMS" preceded by two more bytes ("MMS" appears at offset 0x4D4D532000 in hexadecimal). This signature lets tools distinguish Compression Kit archive files from other compressed C64 formats.

How to open CKIT files

Important: Different programs may use files with the CKIT file extension for different purposes, so unless you are sure which format your CKIT 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 31, 2026

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