How to back up the same iCloud Photo Library from different devices
If you have a very large iCloud Photos library, you may want one device or workflow to create the first archive, then use your iPhone for later incremental backups to the same external drive. The safest way to do that is to split the archive by date range.
Quick answer
Yes, you can use one external drive as the home for the same iCloud Photo Library archive, even if the first large copy and later iPhone backups happen from different devices or workflows. Do not treat it as one shared cross-device incremental task. Use non-overlapping date ranges: first archive everything up to a cutoff date, then use AmberTime on iPhone for everything after that date.
Why this comes up
Large iCloud Photos libraries can be hundreds of gigabytes or several terabytes. The first external backup may take the longest because every original photo, video, Live Photo, RAW file, or ProRes clip needs to be copied or downloaded first.
After that first archive exists, the user often wants a lighter routine: connect the same external drive to an iPhone, back up only recent photos, and avoid copying the whole library again. That is exactly where date ranges are useful.
The safe workflow: split by date range
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Choose a cutoff date
Pick a clean boundary, such as May 31, 2026. The first archive covers everything on or before that date. Later AmberTime backups start on the next day, such as June 1, 2026.
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Create the initial archive
If your first archive is created with AmberTime on iPhone, create a Photo Library task for everything before the cutoff date. If your first archive is created by another Apple workflow, keep that copy on the same drive in a clearly named folder and verify it before moving on.
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Create an AmberTime task for new photos
On iPhone, connect the same drive, create a new AmberTime Photo Library task, and set the date range to start the day after the cutoff. This makes the iPhone task responsible only for the newer part of the library.
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Keep future runs incremental
Run the iPhone task whenever you want to update the archive. AmberTime keeps a backup record for that task, so later runs transfer only new items in that date window.
Example: a 1.5 TB iCloud Photos library
Suppose your iCloud Photos library is 1.5 TB and the first archive should cover everything through May 31, 2026. Put that first archive on the external SSD and label the folder clearly, for example:
Initial-iCloud-Photos-through-2026-05-31
Then connect the same SSD to your iPhone and create an AmberTime task for Photo Library items from June 1, 2026 onward. That task can write to the same drive, but it should have its own destination folder or AmberTime task folder so the archive stays easy to inspect later.
This avoids planned overlap. The first archive owns the older window; the AmberTime iPhone task owns the newer window.
What not to assume
Do not assume that one incremental backup state automatically moves between different devices or unrelated backup tools. AmberTime incremental backup is designed around a task record. Within that task, later runs can skip items already backed up.
For cross-device archive plans, date ranges are more reliable because they make the boundary explicit. You are not asking two devices to agree about every prior item; you are telling each task which part of the timeline it owns.
What about iCloud-only originals?
If Optimize iPhone Storage is enabled, some originals may live only in iCloud. When AmberTime backs up those items and you choose to include iCloud-only originals, iOS may need to download the full-resolution original from Apple before AmberTime writes it to the drive.
That download uses network access. AmberTime still does not upload your files to AmberTime servers, does not require an AmberTime account, and writes the final backup locally to your external drive.
Edge cases to plan for
Edits to old photos
Date ranges are based on the photo timeline. If an old photo is edited after the cutoff date, it may still belong to the older date window. If edits to older photos matter, plan an occasional review or backfill run for the older range.
Duplicate boundaries
Use one clean boundary and avoid overlapping ranges. If the first archive covers through May 31, start the next task on June 1. Do not create one task through June 1 and another starting June 1 unless you intentionally want overlap.
Drive format
For large iCloud Photos libraries, use APFS or exFAT when possible. FAT32 has a 4 GB single-file limit, which can affect large videos, ProRes clips, and some creator media.
FAQ
Can I use the same external drive?
Yes. The same external drive can hold both the initial archive and the later AmberTime iPhone backups. Use clearly separated folders or task destinations so you can understand the archive later.
Will this create duplicates?
Non-overlapping date ranges avoid planned duplicates. For example, one archive through May 31 and one task from June 1 onward have a clear handoff.
Is this the same as automatic cross-device incremental backup?
No. It is a safer archive plan based on date ranges. AmberTime incremental backup remains strongest within the same task, while date ranges make cross-device or mixed-workflow archives predictable.