C4M File

What are C4M files and how to open them

Are you having problems opening a C4M 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 C4M files.

What is a C4M file?

C4M files have multiple uses, and 16bit COM Executable Com4Mail is one of them. Read more about the other uses further down the page.

16bit COM Executable Com4Mail

We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

How to open C4M files

Important: Different programs may use files with the C4M file extension for different purposes, so unless you are sure which format your C4M 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 25, 2026

All known file formats using extension .C4M

While 16bit COM Executable Com4Mail is a popular type of C4M-file, we know of 2 different uses of the .C4M file extension. Different software may use files with the same extension for different types of data.

Clonk Material Definition

Clonk Material Definition files describe how each material in a Clonk game landscape looks and behaves. They are used both in the original Clonk and its open‐source continuation OpenClonk to define material properties like name, color, density, and how materials interact (e.g. whether they can be dug, blown up, emit light). Designers and modders create or edit these files when customizing or adding new material types for landscapes.

These files are written by content creators/modders and loaded by the Clonk game engine when a scenario or map is run. They allow defining up to 125 different landscape materials per scene, and certain essential materials (such as Water, Earth, Snow, Granite, Sand, Tunnel, Vehicle) must always be present. Alongside these definitions, corresponding texture image files are used to depict the materials visually. The engine accepts both PNG textures or uncompressed 256-color BMPs meeting power-of-two dimensions.

Internally, material definitions are plain text. The file begins with a section called [Material] and contains lines giving parameter names followed by values. Typical keys include Name, Color, Density, Friction, MaxAirSpeed, MaxSlide, and others defining both physical behavior and gameplay interactions. The signature "[Material]" at the start and presence of keywords like MAXSLIDE, MAXAIRSPEED, DENSITY, COLOR, NAME help the engine recognize the file.

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!

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