Shared Folders: keeping a folder the same on two Macs

Collab Sync keeps a folder the same on two Macs that both run Storage Studio and are paired with Bridge. A change on one Mac is copied to the other, directly between the two Macs rather than through a cloud service. If both Macs change the same file, the newer version is kept and the other is saved, so nothing is lost.

Two ways to share a folder between Macs

• Share a folder — on a paired Mac's card in the Devices tab, Folders you share with Mac › Add folder… lets the other Mac open that folder from its Finder. New shares are read-only; switch on Write to let the other Mac change the files. The files stay on your Mac.
• Collab Sync — keeps a full copy of the folder on both Macs and keeps them matching. Use this when both Macs need the files even while they're apart.

Setting up a synced folder

In the Collab Sync window, click Add a synced folder. It's only available once another Mac running Storage Studio is paired.

1. Sync with — choose the other Mac.
2. This Mac's folder — click Choose… and pick the folder.
3. Direction — Both ways, This Mac → other Mac, or Other Mac → this Mac.
4. Click Review. Storage Studio checks the folder and shows This is what will mirror: its size, how many files, and how many hidden or cache items will be skipped.
5. Click Send request. The pair shows Waiting for Mac to accept… and nothing syncs yet.

On the other Mac, the request shows as Mac wants to sync a folder with you. Its owner clicks Review, chooses where to keep the folder with Choose…, and clicks Grant — or Decline. They can narrow the direction you asked for, but never widen it.

%% caption: How a synced folder is set up, and what happens when both Macs edit the same file
flowchart TD
  A[Add a synced folder, then Review] --> B{Is the folder allowed?}
  B -->|No| C[Blocked with a reason, pick another folder]
  B -->|Yes| D[Send request]
  D --> E[The other Mac chooses where to keep it, then Grant]
  E --> F[Changes copy across between the two Macs]
  F --> G{Same file changed on both Macs?}
  G -->|No| F
  G -->|Yes| H[Newer version kept, the other saved for Review]

Which folders can be synced

To keep you safe, some folders are refused outright, with the reason shown in red:

• your whole Home folder, or a disk or system folder — Choose a folder a few levels deep — not a disk or system root.
• top-level folders such as Documents, Desktop or Downloads themselves — pick a folder inside them instead;
• a folder Storage Studio itself manages for moves to your external drive.

A folder over 25 GB or 50,000 files needs a second tick: Sync it anyway.

Inside a synced folder, hidden files, Finder's own files, caches and half-written temporary files are skipped. A file is also left until it's closed, and until it hasn't changed for 10 seconds, so half-saved work isn't copied.

Deletes are your choice

In Both ways mode, deleting a file on one Mac does not delete it on the other. In a one-way sync you can switch on Also remove files on the other Mac when I delete them here. It's off by default, and even then the file goes to the other Mac's Trash, so it can be recovered. If a very large number of deletes arrive at once, Storage Studio skips them and tells you, rather than emptying the folder.

When both Macs edit the same file

You'll see A file changed on both Macs (or how many). The newer version was kept automatically. Click Review to see each one: Restore puts the other version back and syncs it, Reveal shows it in Finder, and Dismiss keeps the newer one. If the other Mac has a file open right now, the pair shows In use by Mac as a warning — you can still edit.

Pausing and removing

Pause and Resume stop and restart one synced folder. The remove button stops syncing it; files already synced are left in place on both Macs.

See also: Bridge: connecting another device · Two-way sync · Copy, Move, Sync or Two-way sync · The Trash and the space it holds