Understanding iCloud Drive and the Optimize Mac Storage Option

When you use iCloud Drive, your files are stored on your Mac, Apple's iCloud Drive server, and also any other Macs using iCloud Drive with your Apple ID. When you save or modify a new file, it is automatically mirrored on the server and your other Macs. If you wish to save storage space on a Mac, you can turn on the Optimize Mac Storage option to have some files automatically offloaded from that Mac, even though they will still be represented by an icon and can be reloaded by simply attempting to access the file.
Video Transcript / Captions
Closed captioning for this video is available on YouTube: Understanding iCloud Drive and the Optimize Mac Storage Option.

So I've seen a lot of questions online recently from people who don't quite understand how iCloud Drive works. How does it sync your files between your Macs. Where do the files go. Where are they really. Here's a presentation that explains it all.

We've got three different things here. We've got somebody who has two Macs. An iMac and a MacBook and there are currently no files on either one. Then there's Apple's iCloud Server and they've set up their Mac to use iCloud Drive. In fact to have Documents and Desktop stored on iCloud Drive. You set this up in System Preferences. Currently they have no files. But let's say they create their first file. Just a small file a text document. We'll call it File A and they create it on their iMac. What's going to happen pretty quickly and automatically is that file is going to be uploaded to Apple's iCloud Server. Now, of course, it depends how fast their connection is. How stable their connection is. But it should pretty quickly go up there and appear there.

Now you're probably not looking in your iCloud Server to see what's up there. You can actually do that by going to iCloud.com and there's a file browser there. But normally you wouldn't pay any attention to that. You would just notice that maybe a few seconds or a minute to two later that file would appear on your MacBook as well. So you seem to have the same file on your iMac and your MacBook. You could say that a copy of it has been put from one place to the other. But these are treated as the same file. So you make a change to it on your MacBook and you see the change on your iMac or vice versa. The change is going to happen in all three places as anything you do to these files is going to sync the File A in your MacBook, your iMac, and Apple's iCloud Server. You don't have to do anything to enable this. It just happens if you have iCloud Drive turned on and you saved this file in iCloud Drive.

So let's say you create a bunch more files. In this case B, C, D, and E and C is going to be a really big one. A big video file or something like that. This will then all sync to Apple's iCloud Server. So all the files will be there first and then to your MacBook. Again this may happen so fast you may not even notice it or if file C is really big it may take a little while for it to happen. But they'll sync across and will be treated on your MacBook and your iMac as the same files. Make changes to one and you'll see it on your other machine as well. Delete one and you'll see it deleted on your other machine as well. These files are all linked. So file D is linked on all three locations.

Now there's an option called Optimize Mac Storage. You can fine that in System Preferences in iCloud Settings. It's under Options for iCloud Drive. Now what this does is it allows your Macs to not have a copy of every single file. So say, for instance, your iMac has a huge hard drive and your filling it up with files over weeks and months. Your MacBook, which has a smaller hard drive, is having trouble keeping up with this because there's not as much room. So your iMac has plenty of free space but your MacBook is getting pretty full.

What you can do is turn on Optimize Mac Storage. Now what will happen is something like this. That file C maybe is a large video file like I said and maybe you haven't accessed it in a while. Your MacBook notices that it's running short of space. So it kind of gets rid of C. Notice it's still in the iCloud Server. It's always going to be there. It's still in iMac because there's plenty of hard drive space there.

But in your MacBook it appears to be there but it's not really there. It's basically like a holofile. It's an icon without a file behind it. When you go to open it, it's going to then go out to the iCloud Service and download that file so then you can open it. So you don't have to do anything special to tell it to download that file. You just open it like a normal file and you would be able to get access to file C. Now, of course, if you're not connected to the internet, say you're taking a plane trip or something like that, then yes it's a problem you wouldn't have access to file C. But if you're connected via WiFi like normal you would have no problem. You would just notice a delay as it went out and grabbed that file. Now as soon as you went to access it, it actually puts it on your drive and now it's normal just like before. But later on if it notices that you're not using file C or one of the other files it will then go and get rid of it again even though it will keep it there. Now let's say file C you haven't used it for a long time on either Mac. It may decide to actually get rid of it in both places if your have Optimize Mac Storage turned on in both places.

So you can have Optimize Mac Storage turned Off on your iMac and it will never do this. Every file will be there all the time. Or you can opt to have it turned On and it will make decisions for your iMac and your MacBook separately of which files it thinks it should have. Over time it may do this for lots of files. It's not just due to the file size, it's also due to the age. So if you haven't accessed file B, even though it is pretty small, but you haven't accessed it in a long time then it may actually kind of, you know, have that as a holo file there not taking up any space and you can easily get it back by just going to open the file. You may not even notice that it is downloading if you have a fast connection and it's a small file. If you go to download it then suddenly it appears there and now since you've used that file recently it's probably going to stay there for a little while.

So you can easily get back to having all your files there by turning off the Optimize Mac Storage if you want. You can turn it On and Off at any time. It doesn't effect what's on Apple's iCloud Server. All your files are always going to be there. It just effects what's stored locally. You can't have any direct control over that. So you can't tell a file, like, I don't need you so you can basically offload right now. It's all decided automatically by Mac OS. So using Optimize Mac Storage is the way to use iCloud to virtually get more hard drive space on your Mac because only the files that you recently used, that it thinks you're going to need, are there stored on your Mac. Everything else is stored on the iCloud Server but will be automatically be downloaded as you need them. So turn that function on if you're running short on hard drive space. But you can leave it off if you've got tons of hard drive space and would rather have complete copies of every file stored in iCloud also saved to your hard drive.

Comments: 23 Responses to “Understanding iCloud Drive and the Optimize Mac Storage Option”

    1 year ago

    The question I haven’t been able to figure out is when it comes to spotlight and indexing files that have NEVER been downloaded from the cloud. In other words if you have optimization turn on for “Mac Book” but the entire file never touched “Mac Book” does that mean the content will not be indexed on “Mac Book”? I think, unfortunately, the answer is yes. Only the name of the file will be in spotlight index until the file gets downloaded. This seems like a drawback.

    John Bedrossian
    1 year ago

    What if you don’t want the file on one computer (but do want it on the original) will it download anyway?or if you delete it from one computer will it delete from both?

    1 year ago

    John: If you want that level of control over exactly which files are where and when, then cloud services are not what you are looking for. You’ll need to manually store them where you want just like you did before cloud services.

    1 year ago

    What are the implications for backup with this system? If you backup your MacBook you may not realize files do not exist until you need them. So travelling with a backup when you know you may be offline part of the time loses value.

    1 year ago

    Ken: I would recommend against trying to use a Time Machine backup as something you count on to access files while offline. Backups are for emergency restoration of your files. If you know you need access to all of your files while offline, then you shouldn’t use the “Optimize” feature at all. Either that, or make sure you have Internet access available when needed. Or, make sure you have specific files on your Mac before losing the access.

    anna schane
    1 year ago

    This was a useful and informative video regarding iCloud Drive. I have been confused about online storage. Your explanation and on screen example makes it very clear. I thank you for all your videos.

    Jim Fassino
    1 year ago

    Will Time Machine backups be affected by choosing Optimization? If the file is not really on my iMac but time Machine backs up may iMac, will it show the file that actually resides only on iCloud, as in the case of the large file C in your example?

    1 year ago

    Jim: Possibly. If a file is not really on your Mac, then it can’t be backed up by TM. But then it also means it does exist on Apple’s servers, so the danger of losing that file is mitigated somewhat. And if you created the file, used it, and then stopped using it for a while, and then it was “optimized” later so not on your drive anymore, then it IS on TM as it would have been saved during that initial activity.
    Now if you have plenty of drive space and you turn on “optimize” then you probably have that file anyway as it won’t be offloaded, so it is backed up. But if you are short on hard drive space and don’t use “optimize” then you would probably be forced to get rid of some files at some point anyway to make room. So which is better, having a file stored on iCloud Drive but not your Mac, and maybe backed up, but maybe not. Or, not having that file at all because you ran out of space and had to delete it.
    I guess the bottom line is that if you want all your files to be on your drive and always backed up, then get a Mac with a large drive or some externals in addition. In that case “optimize” is not for you. That’s why it is an option you can turn on or off.

    Don Smith
    1 year ago

    This requires the same Apple ID on all devices. I learned this morning with the Beta update of High Sierra that Messages will be sync’ed to the cloud, except I got the alert that my logins between Messages and iCloud didn’t match. Same Apple ID but different extensions. iCloud was @mac.com and Messages was using @me.com. I always thought they were interchangeable. I logged out of Messages (in its Preferences) and logged back in with @mac.com to match my iCloud login and all was good. FYI.

    Jai Uttal
    1 year ago

    Hi Gary,
    Does this also apply to iOS? I do a ton of music work on my iPad and my storage is almost full. Can I turn on iCloud Drive and optimization on my iPad?

    1 year ago

    Jai: iCloud Drive on your iPad doesn’t download the files at all until you try to access them there. They appear in the list, but the data inside the files isn’t on your iPad until you try to open them.

    1 year ago

    Very informative! As a new Mac user, this certainly cleared up some of the iCloud mystery.

    John Viggers
    1 year ago

    Thankyou, that is a really helpful explanation.

    1 year ago

    I use iCloud as my “main storage” area. I have it in the Favorites panel of Finder. I do this so I know that they will be safe if say my iMac disappears. Is this the right thing to do? I rent the 50G from Apple but I have a lot more than 50G on my iMac. My music is close to 80G alone.
    I liked the video especially the graphics made it very clear. But the question arises, if one has a half a terabyte on their iMac, how does Apple store all of it as per the video?
    Thanks for all the help.

    1 year ago

    Great video. Thank you!
    I have the same question as Gene but I don’t see any reply from you. Help?

    1 year ago

    Gene and Tom: Using iCloud Drive this way is exactly what it is designed for, yes. Chances are your music is either matched with Apple Music or iTunes Match, so it doesn’t take up any of your 50GB. But you can check easily enough at iCloud.com.
    Cloud servers have no problem with 500GB of data as long as you have the fast bandwidth to handle it on your end. Apple’s servers are big, and probably Amazon’s and Google’s are even bigger. 500GB is a drop in the bucket (or ocean) to them.

    Dave Hall
    1 year ago

    Icloud and Keychain is a mystery to me. I clicked on Keychain in the iCloud options expecting all my passwords to be synchronised between my devices, all with Keychain selected, but it seems some keychain items are retained only on the individual machines.
    How does this work. Another thing is I am into RAW photo processing and am running up against RAM capacity issues. Does cloud storage as you describe ( similar too for Dropbox) take up hard drive or RAM storage on the individual machines?

    1 year ago

    So for Keychain, are you talking about your Safari passwords? If so, make sure you have iCloud Keychain turned on for all your devices. It is an individual setting for each one.
    RAM is computer memory, the fast memory used by apps while they are running. This is different than storage which is your hard drive (or SSD). iCloud is storage, not RAM. Yes, it does take up storage on your Mac. Watch the video again because that is what I am explaining.

    Dave Hall
    1 year ago

    Tnks for that. I keep all my pswords on Keychain and three devices are enabled (iMac, Ntbook and iPad) No consistency between machines- I don’t have enough space to explain it all but there are 5 “keychains” in – Login,Micro certs, System, iCloud and system roots, on iMac ( 4 on Ntbook) , as well as 6 “Categories”. Ignoring system generated tokens, etc. how does it all work? I think a good subject for a tutorial!

    1 year ago

    Dave: Sounds like you are overthinking it. Most people, even me, rarely look in Keychain Access at all. Just use Safari to store and view passwords on all devices.

    11 months ago

    Excellent tutorial thank you Gary I should have watched this ages ago.

    Chuck Shopmeyer
    11 months ago

    Does this work for photos as well? My wife’s MacBook Air doesn’t have a lot of storage and was wondering if I made a photolibrary on the iCloud drive and moved her photos there, would that work?

    11 months ago

    Chuck: Yes, the same concept for photos. Just make sure you have the “Optimize” option on in Photos, Preferences, iCloud so her Mac knows it can optimize storage. You don’t need to make a new library and “move” the photos. You just need to enable iCloud Photo Library. See https://support.apple.com/en-us/HT204264

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