CMX File

What are CMX files and how to open them

Are you having problems opening a CMX 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 CMX files.

What is a CMX file?

CMX files have multiple uses, and Corel Metafile Exchange Image is one of them. Read more about the other uses further down the page.

Corel Metafile Exchange Image

These CMX files contain the image data and metadata that describes an image used by Corel Presentations, a presentation software. You can convert these image files into JPG files.

How to open CMX files

Important: Different programs may use files with the CMX file extension for different purposes, so unless you are sure which format your CMX file is, you may need to try a few different programs.

While we have not verified the apps ourselves yet, our users have suggested ten different CMX openers which you will find listed below.

Last updated: August 31, 2026

All known file formats using extension .CMX

While Corel Metafile Exchange Image is a popular type of CMX-file, we know of 2 different uses of the .CMX file extension. Different software may use files with the same extension for different types of data.

OCaml Bytecode (native Object)

OCaml Bytecode (native Object) files are produced by OCaml's native code compiler as part of its workflow for creating optimized executable programs. Each such file describes a single compilation unit (module), supplying information that enables efficient linking and cross-module optimizations when building larger systems.

The native compiler (ocamlopt) compiles OCaml source files (.ml) into two companion outputs: a native object file containing machine code (.o) and a .cmx file holding metadata used in later compilation and linking phases. This metadata includes details about dependencies on other compilation units, interface descriptions (.cmi), which functions are available for inlining, symbol naming, and information needed for packing modules into libraries or other compound units.

During linking, .cmx files from all relevant modules are used alongside their object files to perform cross-module inlining and other optimisations that improve execution speed and reduce overhead. Some compiler options (such as -opaque) control whether or not such cross-module information is included or required, which can affect compilation speed and executable performance.

In the file's internal structure, the format begins with a specific header, Caml1999Y in ASCII at the very start of the file, to identify it as a native-object compilation unit descriptor. Detailed contents include an exported record listing imported units, exported definitions, symbol prefixes, and exported function metadata (e.g. arities, direct entry points). Checksums (MD5) of its own data and dependencies ensure consistency.

Various apps that use files with this extension

These apps are known to open certain types of CMX files. Remember, different programs may use CMX files for different purposes, so you may need to try out a few of them to be able to open your specific file.

Help us help others

File.org helps thousands of users every day, and we would love to hear from you if you have additional information about CMX file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.