At a glance
Firewatch has a Mac version: Steam sells it for macOS. The Mac requirements list only Intel: on Apple Silicon Rosetta 2 runs it, and old Mac versions sometimes do not start on current macOS. Try it in Steam for Mac first.
Firewatch came out on Steam on 9 February 2016, made by Campo Santo.
What your Mac needs
The Mac requirements list only Intel.
Minimum macOS in the Steam requirements: 10.8.
Steam requirements list at least 6 GB of memory for Firewatch.
Allow about 4 GB of disk space for the Mac version.
How to play
Open Steam for Mac and install Firewatch as usual.
If the Mac version will not start, you can install the Windows version through Uncork: download Uncork, sign in to Steam and install Firewatch from there (4 GB). We have not tested it ourselves.
The Windows version through Uncork needs a Mac with Apple Silicon (M1 or newer).
Firewatch uses DirectX 11: Uncork renders it with D3DMetal.