You signed up for Dropbox “because it’s basically free storage,” and now your Mac’s disk is being eaten by… a mirror of the cloud. Sync folders keep a full local copy of every file so you can open them offline — but if you never open 95% of them, you’re renting your SSD to the cloud provider.

The fix is both the most unpopular and the most effective: smart sync / Files On-Demand. Here’s how to enable it per service and reclaim the space.

First: are your sync folders the problem?

du -sh ~/Dropbox
du -sh ~/OneDrive*
du -sh ~/Library/CloudStorage  # Google Drive, OneDrive, and others
sudo du -sh /Applications

If ~/Dropbox is 60 GB while your actual favorite files are 2 GB, that’s the problem.

The fix per service — turn on Files On-Demand

Dropbox — Smart Sync

Open Dropbox → side menu → Preferences/Preferences… → Sync → Sync Settings.
Enable Smart Sync (or Online-only default).
Files become online-only placeholders; local copies are removed; a cloud icon shows the rest.
Right-click any file → Download to bring it local when you need it.

This gives back the disk space without deleting anything from your Dropbox — the data stays in the cloud.

Microsoft OneDrive — Files On-Demand

OneDrive → ⚙️ gear → Settings → Sync and back up → Advanced settings → Files On-Demand.
Set “OneDrive to this device” to Online-only (default for new installs).
Files show a cloud icon; open/download on demand.

Google Drive — Mirror vs stream

Google Drive for desktop has two modes. Switch to streaming:

Google Drive → gear → Preferences → Google Drive → “Stream files” (instead of “Mirror files”).
In stream mode, files are on-demand, not fully mirrored.

iCloud Drive & Photos

iCloud Drive: System Settings → Apple ID → iCloud → Optimize Mac Storage.
iCloud Photos: Photos → Settings → iCloud → Optimize Mac Storage (full guide).

Painless, no file loss — the honest tradeoffs

	Before (mirror)	After (on-demand)
Local disk used	Every file	Only files you use
Open offline	Always	Only downloaded ones
Data safety	Local copy	Cloud copy (backup separately!)
Sync “instant”	Full local	Fewer local files sync

The one non-negotiable: on-demand means “offline availability” is lost for files you didn’t download. If you’re on spotty WiFi, keep your truly-needed folder content local (Right-click → Make available offline / Download).

Synced files are not a backup, either — this change doesn’t make losing data more likely, but you should still have a real backup (Time Machine) regardless.

Clear the synced footprint (already-on-disk files)

Switching to on-demand removes most local copies automatically, but leftover ~/Library/CloudStorage caches and partial mirrors remain. After switching, restart the app and check:

du -sh ~/Library/CloudStorage/*

You can then clear non-local placeholders’ leftover data via the client’s sync settings — do not delete the folders manually, or the client will re-sync or you’ll break the placeholder mapping.

The most overlooked part: multiple accounts & old apps

Old/secondary accounts: remove from the client (Settings → Accounts → Remove) — their local mirrors vanish.
~/Library/Application Support/Dropbox and OneDrive caches can linger: size them, then prune safely with our ~/Library guide.

See it, then fix it

“Do I actually have 60 GB in Dropbox?” should take one glance, not a du marathon. A disk analyzer maps your whole drive by byte cost — ~/Dropbox, ~/Library/CloudStorage, Photos, Docker, node_modules all on one treemap. Then you enable on-demand on exactly the folders that matter, and watch the numbers fall.

DiskInsight scans 100% locally, shows every hidden folder’s true size, stages anything to the Trash for review, and never deletes what you didn’t approve. No telemetry, no cloud — the irony of a cloud-bloat fixer that phones home would be too much.

TL;DR

Find the big mirrors: du -sh ~/Dropbox ~/OneDrive* ~/Library/CloudStorage.
Enable Smart Sync / Files On-Demand / Stream in each client.
Keep essential folders offline-available.
Reclaim the local mirror gigabytes — your cloud files are untouched.

Cloud sync should be a service, not a disk tax.

Get DiskInsight Pro · $9.99 one-time to see which sync folder is the culprit. Start with the full cleanup guide.

Dropbox, OneDrive and Google Drive Are Bloating Your Mac