# Clarification: Interaction between CMAKE\_POLICY\_VERSION\_MINIMUM and cmake\_minimum\_required()
**URL:** https://discourse.cmake.org/t/clarification-interaction-between-cmake-policy-version-minimum-and-cmake-minimum-required/15183
**Category:** Usage
**Created:** [September 19, 2025, 4:33pm UTC](https://discourse.cmake.org/t/clarification-interaction-between-cmake-policy-version-minimum-and-cmake-minimum-required/15183 "2025-09-19T16:33:40Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@perseoGI](https://discourse.cmake.org/u/perseoGI)
#### Post date: [September 19, 2025, 4:33pm UTC](https://discourse.cmake.org/t/clarification-interaction-between-cmake-policy-version-minimum-and-cmake-minimum-required/15183/1 "2025-09-19T16:33:40Z")
Hi CMake team,
Conan member here!
I’d like to clarify the intended behavior of `CMAKE_POLICY_VERSION_MINIMUM` when it is set to a version lower than the one explicitly specified by `cmake_minimum_required()`.
Given the following example:
```auto
cmake_minimum_required(VERSION 3.25)
project(example)
message(STATUS "CMAKE_VERSION = ${CMAKE_VERSION}")
message(STATUS "CMAKE_MINIMUM_REQUIRED_VERSION = ${CMAKE_MINIMUM_REQUIRED_VERSION}")
message(STATUS "CMAKE_POLICY_VERSION = ${CMAKE_POLICY_VERSION}")
message(STATUS "CMAKE_POLICY_VERSION_MINIMUM = ${CMAKE_POLICY_VERSION_MINIMUM}")
foreach(p CMP0048 CMP0077 CMP0127)
cmake_policy(GET ${p} val)
message(STATUS "${p} = ${val}")
endforeach()
```
Configured with:
```auto
$ cmake -DCMAKE_POLICY_VERSION_MINIMUM=3.5 ..
```
I get the following output:
```auto
-- CMAKE_VERSION = 4.1.1
-- CMAKE_MINIMUM_REQUIRED_VERSION = 3.25
-- CMAKE_POLICY_VERSION =
-- CMAKE_POLICY_VERSION_MINIMUM = 3.5
-- CMP0048 = NEW
-- CMP0077 = NEW
-- CMP0127 = NEW
```
From the docs, I understand:
- `cmake_minimum_required(VERSION X.Y)` sets all policies up to X.Y to NEW.
- `CMAKE_POLICY_VERSION_MINIMUM` only takes effect when no explicit minimum is given.
But in this case, even though I explicitly set `CMAKE_POLICY_VERSION_MINIMUM=3.5`, the `cmake_minimum_required(3.25)` call seems to completely override it, resulting in all policies up to 3.25 being set to NEW.
Is this the intended behavior, i.e. that `CMAKE_POLICY_VERSION_MINIMUM` is ignored whenever `cmake_minimum_required()` is called, even if it specifies a higher version?
Or should `CMAKE_POLICY_VERSION_MINIMUM` still constrain the effective minimum (e.g. lower it back down to 3.5)?
### **Use case**
I’m experimenting with always setting -DCMAKE\_POLICY\_VERSION\_MINIMUM=3.5 when building external projects (to ensure future CMake 4.x compatibility).
I’d like to confirm that this does not unexpectedly “downgrade” the policies if the project has already declared a higher `cmake_minimum_required()`.
Thanks for clarifying!
---
### Author:  [@craig.scott](https://discourse.cmake.org/u/craig.scott)
#### Post date: [September 19, 2025, 9:45pm UTC](https://discourse.cmake.org/t/clarification-interaction-between-cmake-policy-version-minimum-and-cmake-minimum-required/15183/2 "2025-09-19T21:45:57Z")
`CMAKE_POLICY_VERSION_MINIMUM` doesn’t unilaterally override the minimum policy version specified by a project. It only raises the project’s minimum if it is less than the version specified by `CMAKE_POLICY_VERSION_MINIMUM`. You can find the relevant code [here](https://gitlab.kitware.com/cmake/cmake/-/blob/v4.1.1/Source/cmPolicies.cxx?ref_type=tags#L313-L319).
> [@perseoGI](#):
>
> I’m experimenting with always setting -DCMAKE\_POLICY\_VERSION\_MINIMUM=3.5 when building external projects (to ensure future CMake 4.x compatibility).
I think you might be misunderstanding what the `CMAKE_POLICY_VERSION_MINIMUM` variable is intended to do. It does NOT ensure future CMake 4.x compatibility. All it does is force projects to use a higher minimum policy version than what the project itself says is safe to use. When you set `CMAKE_POLICY_VERSION_MINIMUM`, you are accepting the risk that the project you are applying it to might not actually handle the NEW policy settings correctly, and things can break in subtle and arbitrary ways. By using `CMAKE_POLICY_VERSION_MINIMUM`, you’re not ensuring CMake 4.x compatibility, you’re blindly forcing projects to use newer policy settings whether they are ready for it or not.
---
### Author:  [@perseoGI](https://discourse.cmake.org/u/perseoGI)
#### Post date: [September 22, 2025, 8:14am UTC](https://discourse.cmake.org/t/clarification-interaction-between-cmake-policy-version-minimum-and-cmake-minimum-required/15183/3 "2025-09-22T08:14:12Z")
Greetings @craig.scott
Thank you very much for your quick response.
This is exactly the clarification we were hoping to receive.
> It only raises the project’s minimum if it is less than the version specified by `CMAKE_POLICY_VERSION_MINIMUM`
I think this same phrase could be added to CMake docs here:
[https://cmake.org/cmake/help/latest/variable/CMAKE\_POLICY\_VERSION\_MINIMUM.html](https://cmake.org/cmake/help/latest/variable/CMAKE_POLICY_VERSION_MINIMUM.html)
On the other side,
> By using `CMAKE_POLICY_VERSION_MINIMUM`, you’re not ensuring CMake 4.x compatibility, you’re blindly forcing projects to use newer policy settings whether they are ready for it or not.
We are aware of the situation. When we raise the minimum CMake version, we first check for any incompatibilities with the existing policies. If there are some, we proceed to apply any necessary patching.
Thank you very much for your time and clarification.