My Mac says that the Startup Disk is full. I know I have way too many pictures in Photos so I got a huge Dropbox subscription to add pics before deleting from my hard drive to free up space. However, now it won't let me download pics since there is not enough free space on the hard drive to do it, so I'm caught in a Catch 22. My ultimate goal is to put pics in Dropbox and external hard drive and delete from computer so that I can have a place to access them when I need them.

  • 1
    Start by moving pictures, and videos if you have them too, to an attached external drive. This will begin to free up disk space on the Startup Disk. Sep 6, 2016 at 2:10
  • 1
    What you could do is turn on selective sync and upload files to dropbox using the web interface. Alternatively you can use a third party service like Arq 5, which lets you back up to dropbox and other services. You can use it without the dropbox app and also if you have the dropbox app installed, you can use selective sync to make sure the backups don't get synced back to the computer.
    – Joonas
    Sep 6, 2016 at 8:07
  • Also, dropbox earlier this year announced a new upcoming feature called project infinite. It allows you to see files in dropbox without taking any disk space.
    – Joonas
    Sep 6, 2016 at 8:26

2 Answers 2


Are you syncing your Photos app using iCloud? Using that in conjunction with the setting "Optimize Mac Storage" should solve your problem (provided you have enough iCloud storage space). When set up this way, Photos stores your entire library on Apple's servers, and only downloads full-resolution photos and videos onto your local hard drive as you view them. If you have a lot of empty space, it'll cache more of them locally, but if you start to run out, it will get purge the high-res versions to make room. The thumbnails remain for browsing.

The big advantage to this over moving things manually onto Dropbox, external drives, etc etc is that your photos and videos stay right there in Photos, and are available on all your Apple devices without any real work on your end. Everything is backed up, and you aren't spending all this time manually shuffling things around. The one (and only, IMO) disadvantage is that you need to pay for whatever level of iCloud storage suits your Photos library size.


Photos is storing all your photographs in a local file in your user folder on your main hard drive. Even when you move a photograph to another location, Photos keeps the photograph in this file unless you delete the photograph from Photos. When you delete a photograph from Photos, the photograph goes to "Recently deleted", but it is still in this local file! You have to delete the photograph from Recently deleted to get that space back. If you do not delete the file, it will delete itself after 30 days — this is the same way Photos works on iOS. If you have a lot of photographs, this file can get really huge.

To locate this file:

  1. Open the Finder
  2. Press Command + Shift + G to open the "Go to the folder:" dialog box.
  3. Type ~/Pictures and click "Go"

This will show you your Pictures folder inside your user folder on your Mac.

The file I am talking about will be called "Photo library" followed by an underscore ( _ ) and the date the library was created (for example: "Photo library_2015.11.05"). However big this file is, it is most likely the source of your problems with not having the free space you expect.

The quickest way to safely free up space is to:

  1. Copy your Photo library file to an external hard drive (if it is a big file, it might take a while to copy over)
  2. Rename the Photo library file so there's no confusion. For example, something like "Photo library_external_drive".
  3. If Photos is open, you will have to quit Photos (Command + Q)
  4. Before opening Photos again, hold down the "option" key — the easiest way to do this is to hold down the "option" key and then click the Photos icon in the Dock. This will open the "Choose Library" dialog.
  5. From the "Choose Library" dialog, click the button that says "Other library..." and choose your external drive, then the Photo library file you just copied over (this is where having renamed the file is useful)
  6. Once you have selected your renamed Photo library file, click "Open"
  7. Verify that all your photographs are there and that everything is right before doing step 8
  8. Go back to the Pictures folder inside your user folder (you could use Command + Shift + G and ~/Pictures again to be sure) and delete the Photo library file (Command + delete). Because you renamed the file on the external drive in step 2, you know that you're not deleting the file you just copied.

To get your free space back you will have to empty the trash. Once that is done, you will get back however much space this file has been taking up on your system.

The next time you open Photos, it will use the new library file that you copied and renamed on your external drive without issue.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .