Steam keeps shader caches and downloads long after the game is gone

How much space does Steam take up on a Mac?

The Steam app is small next to the games: almost all of the space is the library in steamapps, plus caches beside it. To see your own total, and the largest games, run:

du -sh ~/Library/Application\ Support/Steam 2>/dev/null
du -sh ~/Library/Application\ Support/Steam/steamapps/common/* 2>/dev/null | sort -h | tail -10

Where are Steam games stored on a Mac?

In ~/Library/Application Support/Steam/steamapps/common, one folder per game. The Library folder is hidden in Finder: choose Go, Go to Folder and paste the path.

How do I check Steam storage on a Mac?

Inside Steam: Steam, Settings, Storage lists every installed game with its size and lets you uninstall from there. It does not show the shader caches, workshop content or interrupted downloads below, which is why the disk total and Steam's total disagree.

How do I get more storage for Steam on a Mac?

Add a library on an external drive: Steam, Settings, Storage, Add Drive, then move games to it from the same screen. Games run from a fast external SSD, and your internal drive keeps only what you play most.

Where it all lives

du -sh ~/Library/Application\ Support/Steam/* 2>/dev/null | sort -h | tail -10
du -sh ~/Library/Application\ Support/Steam/steamapps/common/* \
  2>/dev/null | sort -h | tail -15

steamapps/common is the games. The folders beside it are the interesting part:

The three folders to check after a clear out

du -sh ~/Library/Application\ Support/Steam/steamapps/downloading \
  ~/Library/Application\ Support/Steam/steamapps/shadercache \
  ~/Library/Application\ Support/Steam/steamapps/workshop 2>/dev/null

Shader caches and interrupted downloads are pure debris once the game is gone, and workshop content can be several gigabytes for a game you stopped playing two years ago. All three are safe to remove; the game reinstalls what it needs.

What not to delete

userdata holds local saves and settings for games that do not use cloud saves. It is small and it is the one folder here that cannot be recreated. Leave it alone unless you have checked that everything you play syncs saves to the cloud.

Uninstalling properly

Use Steam's own uninstall rather than deleting a folder from common, because Steam otherwise still believes the game is installed and shows it as broken. From the library, right click the game, Manage, Uninstall.

Once the library is dealt with, the same question applies to everything else on the Mac: a game folder is a large obvious thing, and the folders that are not obvious are usually where the rest of a full disk is.