# MACHO_COMPATIBILITY_VERSION

New in version 3.17.

What compatibility version number is this target for Mach-O binaries.

For shared libraries on Mach-O systems (e.g. macOS, iOS) the `MACHO_COMPATIBILITY_VERSION` property corresponds to the compatibility version and `MACHO_CURRENT_VERSION` corresponds to the current version. These are both embedded in the shared library binary and can be checked with the `otool -L <binary>` command.

It should be noted that the `MACHO_CURRENT_VERSION` and `MACHO_COMPATIBILITY_VERSION` properties do not affect the file names or version-related symlinks that CMake generates for the library. The `VERSION` and `SOVERSION` target properties still control the file and symlink names. The `install_name` is also still controlled by `SOVERSION`.

When `MACHO_CURRENT_VERSION` and `MACHO_COMPATIBILITY_VERSION` are not given, `VERSION` and `SOVERSION` are used for the version details to be embedded in the binaries respectively. The `MACHO_CURRENT_VERSION` and `MACHO_COMPATIBILITY_VERSION` properties only need to be given if the project needs to decouple the file and symlink naming from the version details embedded in the binaries (e.g. to match libtool conventions).