Cloud accounts · Cloud files and your Mac's space
If I delete a file from my Dropbox, Google Drive or OneDrive folder, is it deleted from the cloud too?
Short answer: Yes — the folder is synced, so deleting there deletes from your account and other devices. To free Mac space without deleting, make the file online-only instead.
Yes. A provider's folder on your Mac is kept in sync with your account, so deleting a file there deletes it from the cloud and from your other devices too. Most providers keep deleted files for a while so you can restore them from their website, but how long depends on the provider and your plan.
If you only want the space back on this Mac, don't delete — make the file online-only instead (Finder's Remove Download, or the provider's own option). It stays in your account and downloads again when you open it.
If you want old files out of the account but kept somewhere, copy or move them to your external drive with Data Transfers first. For iCloud, see deleting online-only iCloud files.