Herein lie multiple single header editions of Outcome:

<outcome-basic.hpp>

An inclusion of basic_outcome.hpp + try.hpp which includes as few system headers as possible in order to give an absolute minimum compile time impact edition of Outcome. See https://github.com/ned14/stl-header-heft.

<outcome-experimental.hpp>

An inclusion of experimental/status_outcome.hpp + try.hpp which is the low compile time impact of the basic edition combined with status_code from https://ned14.github.io/status-code/. If you are on an embedded system where binary bloat must be absolutely avoided, and don't mind the potentially unstable status_code, this is definitely the edition for you.

<outcome.hpp>

An inclusion of outcome.hpp which brings in all the specialisations for the std STL types, the utilities header, plus iostreams and coroutines support. If you don't know which edition to use, you should use this one, it ought to "just work".