Overview
Folder Sync compares two folders and shows you the differences: which files exist on only one side, which are newer on one side, and which are the same. Each difference gets an action automatically, so one click on Synchronize brings both folders up to date.
Folder Sync works with folders on your Mac and on mounted network shares (SMB, AFP, NFS). It doesn’t compare folders on SFTP, FTP or cloud servers.
Starting a Comparison
- Navigate to the first folder in the left pane
- Navigate to the second folder in the right pane
- Open Tools → Folder Sync…
- Click Compare
The window starts with the two pane folders filled in as Left and Right. To pick other folders, use the Browse… button next to each one. The ⇄ button swaps the left and right folders.
Understanding the Results
Each row shows the file’s name, its size and modified date on each side, and the action that will be taken. The status is colour-coded:
| Green (Left only) | File exists only in the left folder |
| Blue (Right only) | File exists only in the right folder |
| Orange (Newer) | File exists in both, and one side has a newer modified date |
| Yellow (Different) | File exists in both with the same date but a different size |
| Gray (Equal) | Same size and modified dates within two seconds of each other |
Folder Sync compares sizes and modified dates. It doesn’t read the files’ contents.
Filtering the list
The filter buttons above the list are All, Different, Left Only and Right Only. You can turn on any mix of them. Equal files are hidden by default; turn on All to show them too.
What Gets Copied
You don’t set a direction by hand. Each row’s action is chosen for you, and the newest file always wins:
- Left only — copied to the right folder
- Right only — copied to the left folder
- Newer on one side — the newer file replaces the older one, which goes to the Trash
- Different, same date — skipped, because there’s no way to tell which one is right
- Equal — skipped
This makes every sync two-way: new and updated files flow in both directions.
The new copy is written in full before the older file is moved to the Trash, so a copy that fails or is cancelled leaves the older file where it was. On a disk without a Trash, such as some network shares, the older file is deleted, as in Finder.
Performing the Sync
- Click Compare and review the results
- Use the filter buttons to show only the rows you want to sync
- Click Synchronize and confirm
Only the rows currently shown in the list are synchronized. For example, to copy only files that are missing on the right, turn on just Left Only before you click Synchronize.
Saving Presets
If you compare the same two folders often, save them as a preset (a “Synclet”):
- Set up the left and right folders and the filter buttons
- Open the Presets menu and choose Save Current as Preset…
- Give it a name and click Save
Choose a preset from the Presets menu to load its folders and filters and compare them straight away. Remove one with Presets → Delete Preset.
Use Cases
Backup Verification
Compare your working folder with a backup on an external drive or network share to see what’s missing or out of date.
Keeping Two Copies in Step
Keep a project folder on your Mac and a copy on a mounted share up to date with each other, with the newest version of each file winning.
Merging Folders
Combine the contents of two folders, keeping the newest version of each file.
Working with a server? Folder Sync doesn’t reach SFTP or FTP servers. To upload changes, open the server in one pane and copy files across with F5.
Where to find it
Tools → Folder Sync… from the menu bar.