Google Drive for Desktop in Streaming mode is supposed to keep files in the cloud; in Mirroring mode everything is local by design. Reality on both: a second cache layer under ~/Library/Application Support/Google/DriveFS grows for months — thumbnails, edit journals and evicted-file stubs — regularly reaching 5-30 GB.

Check yours

du -sh ~/Library/Application\ Support/Google/DriveFS 2>/dev/null

The supported way to shrink it

1. Quit Drive from the menu bar (Pause → Quit, not just close the window).
2. Relaunch with the hidden flag: open -a \"Google Drive\" --args --startup_mode=false — or simply sign out and back in from Preferences, which clears the content cache as part of account teardown.
3. For a hard reset: Preferences → gear icon → Quit, delete DriveFS, sign in again. Files re-stream on demand; nothing in the cloud is touched.

Never delete DriveFS while the app is running — that is how sync databases corrupt.

Mirroring vs Streaming, honestly

Mirroring gives you an ordinary folder (backups love it) but doubles storage for anything also kept elsewhere. Streaming saves disk but couples your work to the network. If your Drive folder is mostly archives, the honest fix is the same one we give iCloud users in the iCloud guide: move archives out of sync folders entirely, keep only the working set.

The rest of the pile

DriveFS joins Telegram (guide), Slack/Discord (guide) and Xcode (guide) on the list of apps that hide gigabytes outside Storage settings. See the cleanup hub for the full map, or check your own numbers with the estimator.