CLI11 provides all the features you expect in a powerful command line parser, with a beautiful, minimal syntax and no dependencies beyond C++11. It is header only, and comes in a single file form for easy inclusion in projects. It is easy to use for small projects, but powerful enough for complex command line projects, and can be customized for frameworks. It is tested on Travis, AppVeyor, Azure, and GitHub Actions, and is used by the GooFit GPU fitting framework. It was inspired by plumbum.cli for Python. CLI11 has a user friendly introduction in this README, a more in-depth tutorial GitBook, as well as API documentation generated by Travis. See the changelog or GitHub Releases for details for current and past releases. Also see the Version 1.0 post, Version 1.3 post, or Version 1.6 post for more information.