This article originally appeared in TidBITS on 2015-04-15 at 7:48 a.m.
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iCloud Photo Library: The Missing FAQ

by Joe Kissell

With the release of Photos for Mac in OS X 10.10.3, Mac users have not only a replacement for the much-maligned iPhoto but also access to iCloud Photo Library, an iCloud feature for syncing photos that Apple introduced in iOS 8.1. In theory, this feature should “just work,” magically syncing all your photos across all your devices. But like so many things in the Apple ecosystem, iCloud Photo Library raises a number of vexing questions, especially for anyone whose use case is in any way atypical.

To Apple’s credit, the company did post an iCloud Photo Library FAQ [1], and it’s worth reading for several basic details. Unfortunately, that FAQ didn’t answer any of the questions I had personally, and judging by the email and comments we’ve received from readers, confusion over this feature is widespread.

I’ve compiled a list of those missing questions, along with answers based on my own testing and research, and the experiences of others on the TidBITS staff and Jason Snell, who’s writing “Photos for Mac: A Take Control Crash Course [2].” If this FAQ doesn’t answer your question — or if my answers don’t match what you’re seeing — please let me know in the comments, and I’ll do my best to update the article accordingly.

Question: What is iCloud Photo Library?

Answer: iCloud Photo Library is an iCloud feature that, when enabled on any given Mac or iOS device, syncs the entire contents of that device’s Photos library to Apple’s servers and thence to any other devices that meet the system requirements, are signed in with the same iCloud credentials, and have iCloud Photo Library enabled.

Q: What are the system requirements?

A: For starters, you need an iCloud account [3], which anyone can get for free. Apple says you must be using OS X 10.10.3 or later on a Mac, and iOS 8.3 on an iOS device. (Even though iCloud Photo Library was available in earlier versions of iOS 8, there were apparently changes in iOS 8.3 that are necessary to make your photos sync with your Mac.) You can also access your photos in the Photos Web app at iCloud.com [4], but only after you have synced the Photos library from at least one device.

Q: Does the Photos Web app let me do everything Photos on my Mac or iOS device can do?

A: No. It’s mostly for viewing photos. You can upload JPEG graphics via the Web too, but not other formats. And you can download and email photos, and mark your favorites. But that’s pretty much it.

Q: Is iCloud Photo Library useful even if I have only one compatible device?

A: Possibly. Because it syncs your photos to the cloud, it provides a backup of sorts. (I definitely would not trust iCloud Photo Library to be my sole backup, but it could come in handy if you have just one device and it’s lost, stolen, or broken.) Having all your photos online also makes sharing a bit simpler, in that you can send someone a link to an existing photo or album in the cloud instead of sending the original photos by email or some other means.

Q: Is iCloud Photo Library free?

A: Sort of yes, but mostly no. iCloud accounts include a paltry 5 GB of free storage, which is shared across all features (including email, iCloud Drive, and iOS backups). Very few people have such small photo libraries that they can fit in the space available for free. As a result, if you want to use iCloud Photo Library, you’ll have to pay Apple for enough extra storage [5] to hold your photo library. You can upgrade to 20 GB for $0.99 a month, 200 GB for $3.99 a month, 500 GB for $9.99 a month, or 1 TB for $19.99 a month. (Those figures are for the United States; prices vary by country.)

Q: Does iCloud Photo Library let me sync my photo library with my spouse or other family member?

A: No. Your iCloud Photo Library is tied to your iCloud username, and is intended for syncing your own photos and videos among your own devices. It is not designed to sync photos between iCloud accounts.

However, iCloud Family Sharing is designed to do exactly that. It creates a Family photo album on each family member’s devices; anything a family member puts in that album (which must be done manually) syncs across all the other family members’ devices. I say more about this in Use iCloud Family Sharing [6], a chapter in my book “Digital Sharing for Apple Users: A Take Control Crash Course [7].”

Q: I thought there was already a photo sync feature called My Photo Stream. How is this different?

A: Since iCloud replaced MobileMe, the service has included a feature that provides limited syncing of photos amongst your devices. It was originally called Photo Stream, and later rebranded to My Photo Stream. My Photo Stream still exists, and you can use it either instead of or in addition to iCloud Photo Library (as discussed later in this FAQ). Although the two services sound superficially similar, and both feature automatic syncing of photos, they differ in many details. Here’s a quick rundown of the major features of each:

iCloud Photo Library:

My Photo Stream:

Q: Can I still use My Photo Stream with Photos?

A: Yes. But if you’re also using iCloud Photo Library, you won’t see a separate My Photo Stream album; all your pictures will appear in All Photos.

Q: If I enable iCloud Photo Library and have adequate storage space, is there any point to keeping My Photo Stream on too?

A: My Photo Stream is still useful if you need to preserve compatibility with devices that don’t meet the system requirements for iCloud Photo Library, and provides a backup method of photo sync in the event that you do hit your iCloud storage limit. Apart from those factors, it’s probably less confusing to stick with just one or the other.

Q: If I use Photos in OS X 10.10.3 or iOS 8.3, am I required to use iCloud Photo Library?

A: Absolutely not. You can leave iCloud Photo Library turned off and continue using and/or syncing Photos exactly as you did with iPhoto or Aperture. If you don’t want to pay for extra storage, or are concerned about exposing your photos to the cloud, or have other concerns based on later answers in this FAQ, you’re under no obligation to use iCloud Photo Library. (For that matter, you don’t have to use Photos at all, if you already have iPhoto, Aperture, or a similar app you like.)

Q: Is there any reason I can’t continue to sync photos via iTunes?

A: If you were previously syncing photos between your Mac or PC and iOS device(s) using iTunes, you can continue doing so with Photos (as long as you have iTunes 12.1.2 or later) and leave iCloud Photo Library turned off. However, if you enable iCloud Photo Library on your Mac, you will no longer be able to sync photos from that Mac with your iOS devices via iTunes.

Q: I heard Apple removed iPhoto and Aperture from the Mac App Store. Can I really keep using them?

A: Yes. Apple no longer offers those apps for sale, but if you already have them installed on your Mac, they will continue to work just as before. Even if you delete them, you should be able to re-download them from the Purchased view in the Mac App Store, although I can’t guarantee that will always be the case. In addition, it’s unlikely that there will ever be updates, so they may cease to work at some point in the future.

Q: What should I do if my photo library is already in iPhoto or Aperture?

A: When you run Photos for the first time, it will ask if you want it to use an existing iPhoto or Aperture library. If you choose to do so, it will import all your photos (in a clever way that avoids duplicating the files on your disk) and then, if iCloud Photo Library is enabled, sync the photos from Photos to the cloud. However, because iCloud Photo Library is not directly compatible with iPhoto or Aperture, any subsequent changes you make to your iPhoto or Aperture libraries will not sync to iCloud Photo Library; you’d have to manually import those new or modified photos into Photos for them to sync.

Q: What if I have multiple Photos libraries?

A: Photos can have just one library open at a time (just like iPhoto and Aperture), but you can have as many different Photos libraries on disk as you like. You can switch to another one either by double-clicking it in the Finder, or by holding down Option when you launch Photos and choosing a different library for that session. But note that only one library at a time can sync to the cloud using iCloud Photo Library — namely, your System Photo Library (see next question).

Q: What is my System Photo Library?

A: It’s the library Photos considers primary, which means, for example, that it’s the one iCloud uses (for iCloud Photo Library, My Photo Stream, and other purposes) and the one iCloud-enabled apps can access. If you have only one Photos library on your Mac, that is by definition your System Photo Library. However, if you have more than one library, you can switch to a different one and designate that library as your System Photo Library by choosing Photos > Preferences > General and clicking Use as System Photo Library.

[image link] [8]

Q: What is iCloud Photo Sharing?

A: iCloud Photo Sharing is a third iCloud photo-related feature, independent from iCloud Photo Library and My Photo Stream, that makes it possible to share special albums called “photo streams” with other people.

Q: What happens if you turn on iCloud Photo Library on multiple Macs or iOS devices, each with an existing, independent Photos library?

A: The libraries merge, regardless of whether they previously overlapped in any way. After everything has synced, the Photos app on each of your devices (and on the iCloud Web site) should contain exactly the same set of photos and videos.

Q: If I enable iCloud Photo Library on multiple devices that already have overlapping photos in their respective libraries, will the resulting merged library contain duplicates?

A: It shouldn’t. In my testing, merging libraries did not result in duplicate images.

As to whether Photos sorts out the duplicates locally or in the cloud, my test results were ambiguous. On one Mac, I turned off iCloud Photo Library, manually uploaded a very large photo to iCloud Photo Library using my Web browser, and also added the photo to Photos manually. Then I reenabled iCloud Photo Library while watching network activity in Activity Monitor, and the amount of data transmitted was only a small fraction of that photo’s size. That test (which I repeated, with variations, several times) implied that before uploading a photo, Photos somehow determines (presumably by means of a checksum [9] or similar mechanism) whether that photo is already in the cloud, and if so, it skips uploading that one — and it does the reverse when considering which images to download.

However, on another Mac, my results were less positive. This Mac started out with a Photos library that greatly overlapped what was already in iCloud Photo Library, yet after I enabled iCloud Photo Library on this second Mac, it transmitted a massive quantity of data over the next couple of days. While the data volume was significantly smaller than the total size of my Photos library, it was also several orders of magnitude larger than what it should have been if only checksums were being transmitted. I can’t account for this difference, because Photos tells me only how many photos are left to be uploaded or downloaded, not which ones (or whether they’re being transferred in their entirety). This lack of transparency is disturbing — a clear indication of exactly what Photos is doing now (and what it did recently) would be welcome.

In any case, if the photos in two locations aren’t identical, you could certainly have duplicates, and I would not be at all surprised if Photos failed at matching duplicates from time to time.

On the plus side, library merging appears to err on the side of data retention. For example, suppose there’s a photo already synced to the cloud. You delete that photo from a non-System Photo Library, and then tell Photos to make that library the System Photo Library. In the process of merging your newly selected library with the cloud, Photos will download the photo you previously deleted, rather than deleting that photo from the cloud. So, you could end up with unwanted photos, but that’s better than not having photos you do want.

Q: What happens if you turn on iCloud Photo Library on a Mac, allow its System Photo Library to sync, and then set a different library as the System Photo Library?

A: First, Photos warns you that switching the System Photo Library will turn off iCloud Photo Library (which is a good thing, because you might want to switch your System Photo Library temporarily without syncing it to iCloud). Assuming you really do want to sync a different library, you must go to System Preferences > iCloud, click the Options button next to Photos, and select iCloud Photo Library to reenable it. (It looks like you can reenable it in Photos > Preferences > iCloud, too, but in my testing, that checkbox had no effect; as soon as I switched panes or closed the window, it deselected itself.) Reselecting iCloud Photo Library also selects My Photo Stream by default, but you can deselect it if you want.

[image link] [10]

Once you’ve reenabled iCloud Photo Library, your newly selected System Photo Library merges with the one already synced to iCloud.

Q: So at that point, after syncing has completed, my new System Photo Library would contain all the photos from my previous library, and I could just delete the old library, right?

A: Yes. But don’t make me remind you about the importance of backups, because something can always go wrong.

Q: What happens if I delete a photo from Photos with iCloud Photo Library enabled?

A: Deleting photos is a two-step process, much like using the Trash in the Finder or in an email app. If you delete a photo from Photos on any of your devices that have iCloud Photo Library enabled, that photo will be moved to a “Recently Deleted” area — not only on that device but also in the cloud and on your other devices. (In Photos on a Mac, choose File > Show Recently Deleted; in iOS, tap Albums > Recently Deleted.) You can retrieve photos from this area before they’re deleted permanently, and if you do, they’ll be restored on all your devices. You can also select one or more photos in this view to delete them permanently, or click Delete All (in Photos on a Mac) to delete them all.

Now, here’s a curious twist. Ordinarily, iCloud Photo Library keeps deleted photos for 30 days, after which it erases them completely and they disappear from the Recently Deleted view on all your devices. But Photos says that the deletion process may itself take up to 40 days (whether you erase a photo from Recently Deleted manually or wait for it to age out). I assume that means Apple still has a copy somewhere — perhaps in a backup — even though you can’t see or access it. So if you’re trying to erase evidence of a crime or indiscretion, you might be out of luck.

Q: What happens to my photos if I sign out of iCloud on a Mac that is (or was) using iCloud Photo Library?

A: Nothing. Your photos stay right in your Photos library. Turning off iCloud Photo Library merely turns off syncing; it does not cause any photos to be deleted from your Mac.

Q: What happens to my photos if I sign out of iCloud on a Mac that is (or was) using iCloud Photo Library and then sign back in using a different iCloud account that already had its own iCloud Photo Library?

A: The two libraries merge for the newly selected iCloud account. That is, Photos on your Mac will, after the sync completes, contain all the photos that were in either library, and so will all the other devices signed in with that Apple ID, with iCloud Photo Library enabled. Meanwhile, the set of photos stored in the cloud for your previously selected iCloud account will remain unchanged, unless you switch libraries again or access that account from another device.

Q: What happens if you pay for iCloud Photo Library storage and then stop paying?

A: Nothing happens to the photos stored on your Mac(s) and iOS device(s). What you pay for is the service of syncing your data to the cloud and storing copies there. If you stop paying, the cloud copy of your library will disappear and your devices will stop syncing, but your local copies remain unchanged.

If all your devices were so low on space that you had no local, full-resolution copies and the originals were stored only in the cloud, that could theoretically leave you with only low-resolution versions of some of your photos. I have found no information on Apple’s Web site about what happens in this situation, but I’d tend to assume the worst. (So, a reminder: back up everything!)

Q: Will iCloud Photo Library be considerate of my bandwidth and data cap?

A: No. Not even remotely. As soon as you turn on iCloud Photo Library, your Mac will start transferring photos to (or from) the cloud as fast as your Internet connection can handle them. If you have a couple hundred gigabytes of photos, they’ll all be uploaded, which could have such unpleasant effects as saturating your Internet connection (and thus slowing down everything you want to do on the Internet with all your other devices) and blowing out your monthly data-transfer allowance in a big hurry (if you have one, as the majority of broadband customers in North America do). It happened to me, and it has happened to other people I know. It’s pretty awful.

Q: So, um… is there anything I can do about that whole bandwidth issue?

A: Yes. First, you can pause transfers. To do this, go to Photos > Preferences > iCloud and click Pause for One Day, which does exactly what it says. (You can manually resume transfers before the day is up by clicking Resume.) But if you need transfers to pause for a longer period of time, you’ll have to click that button every day. Your second option is to temporarily disable iCloud Photo Library altogether by going to System Preferences > iCloud, clicking the Options button next to Photos, and deselecting iCloud Photo Library. There’s no penalty for doing so; this merely disables syncing, and does not affect any photos on your Mac (except that if iCloud Photo Library has downloaded low-resolution versions of any photos but not the full-resolution copies at the moment you disable syncing, Photos may delete the low-resolution versions, and will warn you that it’s about to do so). If and when you later reselect it, syncing will resume.

[image link] [11]

But what if you quit Photos? Won’t that also stop syncing? Maybe. My initial experiments showed that transfers did indeed stop when I quit Photos. After Jason Snell pointed out that he had different results, I ran more tests. My revised results suggest that downloads from iCloud Photo Library pause when you quit Photos, but uploads continue even when the app isn’t running. Furthermore, My Photo Stream (if enabled) may transfer photos when Photos isn’t running. All that to say: quitting Photos might help in certain situations, but you can’t count on it.

Q: Could I avoid the bandwidth problem by enabling Optimize Mac Storage?

A: Probably not. iCloud Photo Library always stores full-resolution photos and videos in the cloud. If you go to Photos > Preferences > iCloud and select Optimize Mac Storage, that means your Mac will download full-resolution copies of any photos added by other devices if there’s enough space; only if you lack sufficient storage space on your Mac will it download lower-resolution copies instead. (And, if this happens, you can still manually download the full-resolution version of any image you want to work with.) In iOS, there’s a similar option that works the same way; go to Settings > iCloud > Photos and select Optimize iPhone (or iPad) Storage.

Q: Will Apple ever fix this problem — for example, by letting me throttle the bandwidth Photos uses?

A: I have no idea.

Q: Are there any other risks to syncing my photos with iCloud Photo Library?

A: There are always risks on the Internet. In particular, anyone who knows (or guesses, or hacks) your iCloud username and password could see all the photos and videos in your library. This is yet another good reason to use a long, random password (see “Take Control of Your Passwords [12]”) and two-step verification (see “Apple Implements Two-Factor Authentication for Apple IDs [13],” 21 March 2013). But if your library contains any photos that could cause significant harm or embarrassment if they were to be made public, the wiser course is not to use iCloud Photo Library at all and sync your photos locally instead.

Q: Should I use iCloud Photo Library or Dropbox, Amazon Cloud Drive, or some other cloud storage method?

A: It depends. If you use only Apple devices — and especially if they’re all running Yosemite or iOS 8 — iCloud Photo Library gives you the most convenient, seamless experience. Other providers, including Dropbox and Amazon Cloud Drive, charge less than Apple does for online storage of photos and videos, and also work on a wider range of platforms. So if saving money is your top priority or you want to sync photos with a Windows or Android device, for example, another service might be a better choice. But the key thing to keep in mind is that iCloud Photo Library is the only cloud storage service that Apple’s Photos app supports. So if you want to use Photos to manage your photos and videos and also have cloud storage and syncing, iCloud Photo Library is definitely the way to go.

[1]: https://support.apple.com/en-us/HT204264
[2]: http://tid.bl.it/photos-crash-course-tidbits
[3]: https://www.icloud.com/
[4]: https://www.icloud.com/
[5]: https://support.apple.com/en-us/HT201238
[6]: http://www.takecontrolbooks.com/resources/0170/site/chap35.html
[7]: http://tid.bl.it/digital-sharing-crash-course-tidbits
[8]: http://tidbits.com/resources/2015-04/PhotosGeneralPrefs.png
[9]: https://en.wikipedia.org/wiki/Checksum
[10]: http://tidbits.com/resources/2015-04/PhotosSwitchSPL.png
[11]: http://tidbits.com/resources/2015-04/PhotosiCloudPrefs.png
[12]: http://tid.bl.it/tco-passwords-tidbits
[13]: http://tidbits.com/article/13654