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Setting Up a New Mac: Should You Migrate or Do a Clean Installation?

Posted on December 18th, 2014 by

Migration Assistant icon

If you’ve just bought a new Mac, and you’re upgrading from an older computer, you want all of your files and data to be accessible on the new machine. But when setting up a new Mac, should you migrate or do a clean installation?

When you buy a new Mac, it might be a good idea to do a clean installation; starting from scratch, with a brand-new operating system, and adding the files that you need manually. Here’s how to migrate your files to your new Mac, or do a clean installation, and the pros and cons of both methods.

How to migrate files to a new Mac

Apple includes a very useful tool as part of its Mac operating system: Migration Assistant. This feature is the same as Setup Assistant, which only runs during the setup of a new Mac; therefore, once you have set up the computer, you will have to use Migration Assistant.

When you set up a new Mac, the Setup Assistant offers to copy your files. To use this tool on a Mac:

    1. Connect two Macs using a Thunderbolt, FireWire, or Ethernet cable.
    2. Connect the new Mac to a hard drive where you have cloned your startup volume (using an app like Intego Personal Backup), or connect it to a drive where you’ve done a Time Machine backup.


    1. Select the Mac or hard drive from which you want to copy data, and then select what type of data you want to transfer—user accounts, applications, other files and folders, and settings—and wait while the files get copied.


As you can see, Migration Assistant is easy to use. The advantage of using this method is that all your files get copied, and that it’s very easy. However, the disadvantage of using the Migration Assistant is that all your files get copied. This is a disadvantage because if you have been upgrading your Macs over the years by installing new versions of OS X over old ones, and migrating data from old Macs to new ones, you’ll have hundreds, even thousands of old files that you no longer need. For this reason, you might want to consider doing a clean installation.

Clean Installation

When you do a clean installation, you let OS X run its Setup Assistant and create a new, empty user account. During the process, you enter some information, such as your Apple ID, so your iCloud account is activated, but, for the most part, your Mac will be a tabula rasa.

If you go this route, you then need to manually copy files from your old Mac, or from a backup. This part of the process can be time-consuming, but it can allow you to sift through your files to find what you really need, and slim down your Mac. I did so this year, for the first time in many years, and many Macs, and was surprised to find how much I didn’t copy.

Here’s what you need to copy after a clean installation:

Applications: OS X installs a number of applications, many of which you probably use every day. These include the Safari web browser, Mail, Calendar, iTunes, iPhoto, and the iWork apps (Pages, Numbers, and Keynote). But you probably use plenty of other apps on your Mac. If you have purchased apps from the Mac App Store, you’ll need to re-download them; if you copy these apps from one Mac to another, they won’t work. But for any apps you’ve purchased directly from developers, it’s easier to copy them manually. And this is a good time to decide which of the many apps in your Applications folder you want to keep. You may find dozens of apps that you rarely use. If so, don’t copy them.

Your Home Folder: you want to copy most of the files from your home folder (that’s the folder with the house icon and your username). You don’t want to copy the folders at the top level of your home folder—Desktop, Documents, Downloads, Movies, Music, and Pictures—but rather the contents of these folders into the identically-named folders on the new Mac. Again, take this opportunity to check whether you need to keep all of the files in these folders.

Your Library Folder: there is a special folder in your home folder called Library. By default, this folder is hidden, but it contains many files that you should copy. For example, all of your email is in this folder, as is the information in the Contacts app. First, you need to access this hidden folder on the new Mac. In the Finder, press Command-Shift-G, and then type: ~/Library. Click Go to view the contents of this folder. In another Finder window, do the same thing to view the old Library folder. Press Command-Shift-G, then enter, for example, /Volumes/backup-disk-name/Users/your-user-name/Library, and click Go. (Type the appropriate names for the backup disk and your user name.) You’ll have two windows open.

Here is a list of folders that you want to copy from the old Library folder to the new one:

  • Application Support; though look inside this folder, and only copy folders for apps you’re still using. Make sure to copy the AddressBook folder in this folder.
  • Calendars
  • Fonts
  • iTunes; this contains iTunes plug-ins, AppleScripts, and iOS updates.
  • Keychains; this contains all your stored passwords.
  • Mail; this contains all your email, and your email settings.
  • Preference Panes; if there are any that you’ve installed that you still use.
  • Safari; this has your Safari bookmarks.

I don’t recommend that you copy the Preferences folder; this probably contains lots of files for apps you no longer use. I do, however, suggest that you go through that folder and copy over any files or folders for apps that you do use, especially if, when you launch them, their setup is different. However, you may just want to manually reset the preferences for your apps; this is a good way to rediscover your apps and their interfaces.

You’ll notice, as you start working with the new Mac, that you will need to enter serial numbers for all of the apps that you did not purchase from the Mac App Store. This is because many apps store invisible files on your Mac for registration purposes, and you haven’t copied these. So make sure you know where your serial numbers are.

As you work on your new Mac, you may find that certain files are missing. For this reason you should absolutely not delete your old backup, and especially the ~/Library folder. You may need to go back into that folder and copy some other files to the new Mac.

While I don’t recommend doing a clean installation for each new Mac you get, or for each OS X update, it’s a good idea to do it every few years. Just make sure to keep a backup in case there are any files you need to find that you didn’t copy over the first time around.

Are you new to Mac?

Want to get the most out of your new MacBook, iMac or other Apple computer? Whether this is your first laptop or you’ve just switched from Windows, there are a few things you should know about your new Mac, like basic keyboard shortcuts or how to use the various features macOS has to offer. Learn more about what your Mac computer can do for you at the Intego New Mac User Center: Get started now!

About Kirk McElhearn

Kirk McElhearn writes about Macs, iPods, iTunes, books, music and more on his blog Kirkville. He is co-host of the Intego Mac Podcast and PhotoActive, and a regular contributor to The Mac Security Blog, TidBITS, and several other websites and publications. Kirk has written more than twenty books, including Take Control books about iTunes, LaunchBar, and Scrivener. Follow him on Twitter at @mcelhearn. View all posts by Kirk McElhearn →