OS X Yosemite: Increase disk space
There are several ways to increase available disk space.
To find out how much disk space you have, open Disk Utility, click your disk (usually named Macintosh HD), then click Info.
Delete files, folders, or apps
In Mail, choose Mailbox > Erase Deleted Items > In All Accounts, and Mailbox > Erase Junk Mail.
You can also check the other apps you use for ways to remove or compress items.
Delete downloaded items
Items you download from the Internet are in your Downloads folder. If you have many unneeded downloaded items, delete them. It’s a good idea to delete items you don’t need in order to free up disk space.
Locate large files
You can find your largest files and then compress them or move them to another disk.
In the Finder, choose Go > Home, or press Shift-Command (⌘)–H.
Choose File > Find, or press Command (⌘)–F.
Click the Kind pop-up menu, then choose Other.
Below “Select a search attribute,” select the File Size checkbox. Make sure no other checkboxes are selected, then click OK.
Change the “equals” pop-up menu to “is greater than,” then change the “KB” pop-up menu to “MB.”
Enter a minimum file size. A good starting point is 100 MB. You can change the value to see more or fewer results.
Searching begins as soon as you type a file size. It may take a moment for all the search results to appear.
Compress files and folders
You can compress files and folders into an archive that takes up less space.
Compress a file or folder: Control-click it or tap it using two fingers, then choose Compress from the shortcut menu.
If you compress a single item, the compressed file has the name of the original item with the .zip extension. If you compress multiple items at once, the compressed file is called Archive.zip.
Uncompress (expand) an item: Double-click the .zip file.
Move files to another disk
Move files and folders you don’t often use to an external disk, or to a disk connected to your AirPort or other network. For more information, see Use external storage devices.
Burn files and folders to a CD or DVD. for more information, see Burn CDs and DVDs.
After the files are copied, you can delete the copies on your Mac.