No official way to install ninja is documented

[marc-hb]

Description

This is a documentation gap; there is no specific category for that so filing as a "bug".

As detailed in #514 (comment) and many others, ninja is probably the most popular tool for building C/C++. It's also used outside C/C++ Unsurprisingly, including ninja in the default image has been requested many times over the years:

• Add Ninja build system to Mac, Linux and Windows #514
• Update/Add Ninja #741
• add ninja build to Linux images #742
• Update/Add Ninja #1531
• Update/Add [tool name] #4972
• windows-2022 image 20230918.1.0 removed the "ninja" tool #8343
• Add ninja #8348

This has been rejected every time. One of the answers given practically every time: "it's easy to install at run time".

Because ninja is the top C/C++ build tool, how to install it should be in the official documentation.
https://docs.github.com/en/search?query=ninja

The official documentation should either:

• provide sample install code that works for each supported operating system + the ${{ conditionals }} to make it portable. Or, much better:
• endorse some official, GitHub-approved action that installs ninja on all operating systems so not every user has to perform a duplicate security audit effort. In other words, officially endorse one of these:
• https://github.com/marketplace/actions/get-cmake
• https://github.com/seanmiddleditch/gha-setup-ninja
• https://github.com/marketplace/actions/install-ninja-build-tool
• ... ?

As of now, installing ninja requires searching closed issues for scattered, conflicting and out of date advice. Random tips to install ninja on Windows vary (either vcpkg that comes and goes, unreliable choco, other?), mac recommendations are very slow (brew) and Linux samples miss the important and non-obvious "apt-get update" pre-requirement #2924

From #8348 (comment)

"The instrument is extremely easy to install in runtime."

I don't think it is "extremely" easy, see above. Especially not on Windows. But if it truly is, then documenting this will be too.

cc: @erik-bershel, @Darleev, @alepauly, @miketimeofeev, @maxim-lobanov, @dibir-magomedsaygitov

Platforms affected

• Azure DevOps
• GitHub Actions - Standard Runners
• GitHub Actions - Larger Runners

Runner images affected

• Ubuntu 20.04
• Ubuntu 22.04
• Ubuntu 24.04
• macOS 12
• macOS 13
• macOS 13 Arm64
• macOS 14
• macOS 14 Arm64
• macOS 15
• macOS 15 Arm64
• Windows Server 2019
• Windows Server 2022
• Windows Server 2025

Image version and build link

This is a documentation gap; there was no category for that.

Is it regression?

No

Expected behavior

https://docs.github.com/en/search?query=ninja shows something

Actual behavior

https://docs.github.com/en/search?query=ninja shows nothing

Repro steps

https://docs.github.com/en/search?query=ninja

[RaviAkshintala]

Hi @marc-hb Thank you for bringing this issue to our attention. We are looking into this issue and will update you on this issue after investigating.

[Toxe]

Thank you for bringing this up. (Even though this shouldn't be an issue in the first place.)

[kelvinphilip889]

It will be rectify soon

[vidyasagarnimmagaddi]

Hi @Toxe ,

• The reference manual for ninja is maintained here, the source code is maintained in this github repo.

• Also, docs.github.com is open source, if you feel a documentation is missing, please raise a PR with your changes on the repo, maintainers would be happy to review your contribution.

• Ninja can be installed at runtime in our runner.

We are closing this issue as it does not pertain to github runner images.Thanks.

[sureshe456]

Hi @marc-hb, I would like to inform you that we are unable to add these tools in the macOS images due to the need to maintain lightweight operating system images and limited sapce.

We request that you use the below code at runtime for your build. Thanks.