---
id: icloud.does-icloud-photos-sync-a-second-photos-library
url: https://storagestudio.us/faq/icloud/does-icloud-photos-sync-a-second-photos-library
category: "iCloud & iCloud Photos"
subcategory: "iCloud Photos and the Photos library"
question: "Does iCloud Photos sync every Photos library on my Mac?"
alt_questions:
  - "Multiple Photos libraries iCloud"
  - "Second photo library not syncing"
  - "Which library does iCloud Photos use?"
  - "System Photo Library meaning"
  - "iCloud Photos only one library"
short_answer: "No. iCloud Photos syncs only the System Photo Library set in Photos → Settings → General. Other libraries stay local. To change it, open that library with Option held and choose Use as System Photo Library."
tags: ["icloud photos", "photos library", "system photo library"]
related: ["https://storagestudio.us/faq/icloud/how-do-i-move-my-photos-library-to-an-external-drive"]
applies_to: "all"
last_reviewed: 2026-10-01
---

# Does iCloud Photos sync every Photos library on my Mac?

No. iCloud Photos only syncs the **System Photo Library** — the one Photos is set to use in **Photos → Settings → General**. Any other library on your Mac or on an external drive stays local and isn't uploaded.

To switch which library syncs, open that library (hold **Option** while opening Photos), then click **Use as System Photo Library**. Be careful: switching can mean a large upload or download, and merging libraries isn't automatic.

If you've moved your library to an external drive, make sure that copy is the System Photo Library, or iCloud Photos won't follow it. See [moving the Photos library](https://storagestudio.us/faq/icloud/how-do-i-move-my-photos-library-to-an-external-drive).