Games on a Mac hide in four places, and only one is obvious

Gaming on a Mac spreads across more places than on a console or a PC, because several of the games are not really Mac software at all. They run through a translation layer that keeps its own copy of a Windows environment, and that copy is where a surprising amount of the space goes.

The four places

# Steam, if it is installed
du -sh ~/Library/Application\ Support/Steam 2>/dev/null
du -sh ~/Library/Application\ Support/Steam/steamapps/common/* 2>/dev/null | sort -h | tail -10

# Translation layer bottles, which are easy to forget entirely
du -sh ~/Library/Application\ Support/CrossOver/Bottles/* 2>/dev/null | sort -h
du -sh ~/Library/Containers/com.isaacmarovitz.Whisky 2>/dev/null

# Everything else large under Application Support
du -sh ~/Library/Application\ Support/* 2>/dev/null | sort -h | tail -12

Bottles are the part people miss

Each bottle is a self contained Windows layout, with its own system files, its own registry and its own copy of any runtime the game needed. Two games in two bottles means two of everything, and a bottle left behind after you stopped playing keeps all of it.

• One bottle per game is the usual advice for compatibility and the worst arrangement for disk space.
• Deleting a bottle removes the game with it, which is what you want when you are finished.
• Saves may live inside the bottle, so check before deleting one you might return to.

Moving a Steam library to an external drive

1. In Steam, Settings, Storage, add a drive and create a second library folder there.
2. Select a game, then Move to relocate it without redownloading.
3. Keep the drive connected and mounted at the same path, or Steam will offer to download the game again.
4. An external SSD is fine for most titles. A spinning disk will show in load times.

App Store and Arcade games are less flexible: they install to the system drive and there is no supported way to move them, so uninstalling and reinstalling is the only lever. That is the same limitation as the Applications folder generally.

What is safe to clear

Shader and asset caches rebuild themselves and are safe to remove when a drive is tight, at the cost of a slower first launch. Game saves usually live in ~/Library/Application Support beside the game, which is why what an uninstall leaves behind matters here more than most places.

Detail on the two largest sources is in Steam games and the other launchers. If the games are Windows ones, Windows apps on a Mac covers what the layer itself costs.