CMA File

What are CMA files and how to open them

Are you having problems opening a CMA 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 CMA files.

What is a CMA file?

A .CMA file is an OCaml Bytecode file.

OCaml Bytecode library files are archive files produced by the OCaml compiler toolchain. They bundle together multiple compiled module object files (in OCaml's bytecode format) so that other OCaml code can link against them as a single library. Such libraries are created when source code has already been translated into bytecode (.cmo files) and then grouped for reuse.

These library archives are built using OCaml's bytecode compiler (ocamlc) with the "-a" option. Once compiled, they are linked into programs by the bytecode linker rather than producing a native binary directly. Execution of code that uses them happens via the OCaml bytecode interpreter, which loads the necessary parts of the library on demand.

Files start with the ASCII signature Caml1999A at offset 0. They are archives of .cmo bytecode objects, and when built with C foreign stubs or custom C libraries, may record linking directives like -custom or -cclib so that users of the library need not re-specify them at link time.

How to open CMA files

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

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

Last updated: August 31, 2026

Various apps that use files with this extension

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

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