Install directory used by install().

If make install is invoked or INSTALL is built, this directory is prepended onto all install directories.

This variable defaults as follows:

  • New in version 3.29: If the CMAKE_INSTALL_PREFIX environment variable is set, its value is used as default for this variable.

  • c:/Program Files/${PROJECT_NAME} on Windows.

  • /usr/local on UNIX platforms.

See CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT for how a project might choose its own default.

On UNIX one can use the DESTDIR mechanism in order to relocate the whole installation to a staging area. See the DESTDIR environment variable for more information.

The installation prefix is also added to CMAKE_SYSTEM_PREFIX_PATH so that find_package(), find_program(), find_library(), find_path(), and find_file() will search the prefix for other software. This behavior can be disabled by setting the CMAKE_FIND_NO_INSTALL_PREFIX to TRUE before the first project() invocation.


Use the GNUInstallDirs module to provide GNU-style options for the layout of directories within the installation.

The CMAKE_INSTALL_PREFIX may be defined when configuring a build tree to set its installation prefix. Or, when using the cmake(1) command-line tool's --install mode, one may specify a different prefix using the --prefix option:

cmake --install . --prefix /my/install/prefix