Start with these three steps
Identify the backup source
Record the disk or network location, the iMac it belonged to and the last successful date. Keep any encryption password available privately.
Choose the required point in time
Write down when the missing files last existed or were correct. A newer backup is not automatically the useful one after an accidental deletion.
Check the source condition
Stop if the backup disk clicks, disconnects or produces repeated errors. Do not erase it to make Time Machine recognise it.
Retrieve a specific item before replacing everything
For a stable backup, open the original folder, enter Time Machine and browse to the relevant date. Apple’s workflow allows selecting individual files or folders; restored items return to their original location. Protect current work before accepting any replacement choice.
For a replacement iMac or a larger rebuild, Apple also describes Migration Assistant recovery from Time Machine. Choose that broader route when you need user accounts and applications, and review the selected source and destination carefully.
Sources: [1] Apple Support [2] Apple Support
Local snapshots share the iMac’s storage risk
Time Machine local snapshots are held on the same disk as the original files. They may help with a recent change when the normal backup disk is disconnected, but they are not an independent copy that survives loss of that physical storage.
Apple says snapshots are removed as they age or space is needed. Avoid storage-cleanup activity while a useful snapshot may be your remaining route.
An existing healthy backup disk may hold an irreplaceable older version. To help preserve that history, inspect it from another working Mac that is not configured to back up to it. Do not adopt it as a backup destination or start a new backup before retrieving the needed files. This is a preservation recommendation: Apple documents that reconnecting an established destination resumes its schedule and that old backups can be removed when it fills.
Sources: [3] Apple Support [4] Apple Support [7] Apple Support
Check what the backup actually contains
For Photos, inspect the library and the original media you need. Apple warns that when Optimise Mac Storage was used, Time Machine may lack the full-resolution originals. Restoring a library is therefore not the same as proving every image and video is available offline.
Make a small verification list across dates and accounts. Check the most recent business file, an older family event and a project with external assets. Open the results on working storage; do not rely solely on folder names or the amount of data transferred.
Sources: [5] Apple Support
A broken backup can become the recovery source
If the original iMac has failed and its only backup is unreadable, treat that backup as valuable source media. Do not repurpose it as a destination for new backups. Keep its original enclosure and power supply and record the errors already seen.
Data Recovery Lab NZ is an external provider with a dedicated Time Machine service covering damaged disks and backup structures, including network sparsebundles. For a NAS backup, ask what information or equipment is needed before removing disks or changing the storage configuration.
Sources: [6] Data Recovery Lab NZ
A realistic view of recovery
- A backup cannot restore an item it never captured, and an available date does not guarantee every file is readable.
- A damaged backup may yield selected files or dates without a complete restorable history.
Your questions, answered
Does Time Machine running on my iMac prove I have an external backup?
Should I start a new backup before looking for deleted files?
Can I recover just my Photos library?
Need help with the original iMac?
Describe the model, what happened and which data matters. Data Recovery Lab NZ is an external specialist; ask it to confirm the assessment route for your exact device.
Sources & further reading
Primary and specialist guidance checked 27 October 2026. Features and instructions depend on the model and operating system.