Once you’re happy with the result, click the “OK” button. Instantly, Preview will tell you the new file size of the image. Then, change the width to around 50% of the original size (You can try out different resolutions.). Then, from the editing options, click the Resize button (It’s the icon with multiple boxes.).įrom the pop-up, first, switch to the “Pixels” option. Click the Edit button from the top toolbar (It looks like a Pen icon.).

Now that the photo is open in Preview, it’s time to resize it. If the disk image will be used with a Mac that has a solid state drive (SSD) and uses macOS 10.13 or later, choose APFS. RELATED: How to Change the Default Application for a File Type in Mac OS X If the disk image will be used with a Mac or Windows computer and is 32 GB or less, choose MS-DOS (FAT) if it’s over 32 GB, choose ExFAT. If Preview is not set as the default image viewer, right-click, and choose the Open With > Preview (We recommend that you take some time to set Preview as the default image viewer, as it will make your life easier.). If you’re trying to upgrade from an earlier version of macOS, you’ll need a whopping 44.5GB of space. Then, simply double-click the file to open it in Preview. Take a look at the system requirements on Apple’s website, and you will see that you need 35.5GB of free space, and that’s if you’re upgrading from macOS Sierra or later.

First, open the Finder app and locate the image (or images) that you want to resize. Using the Preview app, you can do this for one image at a time or for multiple images at once.

Mac disk image size