# CMP0147

New in version 3.27.

Visual Studio Generators build custom commands in parallel.

Visual Studio 15.8 (2017) and newer support building custom commands in parallel. CMake 3.27 and above prefer to enable this behavior by adding a `BuildInParallel` setting to custom commands in `.vcxproj` files. This policy provides compatibility for projects that have not been updated to expect this, e.g., because their custom commands were accidentally relying on serial execution by MSBuild.

The `OLD` behavior for this policy is to not add `BuildInParallel`. The `NEW` behavior for this policy is to add `BuildInParallel` for VS 15.8 and newer.

This policy was introduced in CMake version 3.27. Use the `cmake_policy()` command to set it to `OLD` or `NEW` explicitly. Unlike many policies, CMake version 3.28.3 does not warn when this policy is not set and simply uses `OLD` behavior.

Note

The `OLD` behavior of a policy is `deprecated by definition` and may be removed in a future version of CMake.