Backups before any bulk operation
Renaming a thousand files, merging an address book, re-encoding a folder of video — bulk operations are where one mistake is multiplied by everything. Here is the thirty-second backup to take first for each kind of data on a Mac.
A single edit that goes wrong is annoying. A bulk operation that goes wrong is a disaster, because the mistake is applied to everything at once — every file renamed wrongly, every contact merged into the wrong card, every photo overwritten with a smaller copy.
The good news is that the protection is cheap. Almost every kind of data on a Mac can be backed up in under a minute, and the moment to do it is immediately before the operation, not in general.
This is advice we follow ourselves, and it is written into how our tools work — but no tool's safeguards replace a backup.
The rule
Before any operation that changes many things at once, make a copy you could restore from — and know how you would restore it.
"Many things" means anything you could not fix by hand in five minutes.
Files and folders
Duplicate the folder. Select it in Finder and press Command-D. On APFS — the file system on every modern Mac — duplicating is nearly instant and uses almost no extra space until the files change, because the copy shares storage with the original.
That makes it the best pre-operation backup there is for a folder of files: fast, free and trivially restorable.
Time Machine. If you use it, trigger a backup just before the operation: Back Up Now from the Time Machine menu bar icon, or in System Settings. A local snapshot can also be created from Terminal:
tmutil localsnapshot
Local snapshots live on your internal disk and are removed automatically after a while, so they are a short-term safety net, not a backup strategy.
Cloud-synced folders have their own version history, but do not rely on it for bulk changes: a thousand renamed files synced as a thousand changes can be hard to roll back through a web interface.
Contacts
File → Export → Contacts Archive… in Contacts. It saves every account's contacts, including notes, in one file, and File → Import restores it.
Do it before merging duplicates, bulk-editing, importing a large file, switching accounts or letting any app make changes across your address book. Restoring an archive replaces the address book with the archived version, so later changes are lost — which is exactly what you want if something went wrong.
If you use iCloud Contacts, iCloud.com also keeps recent archives under Data Recovery → Restore Contacts, as a second line of defence.
Photos
Before bulk edits in the Photos app, your originals are generally safe — Photos keeps them and lets you revert edits. The risk is operations outside Photos on exported files: resizing, converting or renaming in bulk. Duplicate the folder first.
For a Photos library itself, Time Machine or a copy of the library file on an external drive before major changes.
Documents and projects
Before a "save as a new version" that overwrites, a batch export that replaces files, or a find-and-replace across many documents: duplicate the folder.
Many Mac apps also keep document versions: File → Revert To → Browse All Versions. Useful, but only for apps that support it, and only for documents you saved in them.
Check the backup exists
A backup you have not checked is a hope. After making one:
- Confirm the copy is where you expect and is the right size.
- For a contacts archive, check the file is not tiny.
- For a duplicated folder, open it and look at a couple of files.
During the operation
- Start with a sample. Run the operation on ten items before the thousand.
- Preview if the tool allows it. Look at all the proposed changes, not the first few.
- Read confirmation dialogs. "Replace" and "Keep Both" are adjacent for a reason.
Afterwards
Keep the backup until you have used the result for a while — a day for a simple rename, a week or two for an address book cleanup. Problems with bulk changes are often noticed later, when you look for something that is no longer where it was.
Then delete it deliberately, rather than leaving a folder called Photos copy 3 for your future self to wonder about.
How our tools approach this
We design around the assumption that bulk operations need safeguards, and that safeguards still need backups underneath them:
- RenameDeck shows every proposed name before renaming, never overwrites an existing file, and keeps journaled history for undo while the renamed file is still the one it renamed.
- Compact Contacts shows exact changes before Bulk Edit saves them, keeps encrypted on-device merge history for undo, and shows which cards are ready, have warnings or are blocked before an import writes anything.
- Ziploom lets you decide in advance how existing destinations are handled, and checks disk space before extraction starts.
Each of those reduces the chance of a mistake and makes many mistakes reversible. None of them is a backup. The thirty seconds before you click are still the best protection there is.