When it's time to move your content to a new Mac, Apple provides Migration Assistant to get the job done. Migration Assistant can migrate data from a Mac, Time Machine backup, or startup disk — even from a Windows PC!
When it works, it works great.
When it fails, it fails miserably.
It doesn't do a very good job of estimating how long the migration will take, and sometimes it can get stuck and never finish.
In most cases, we recommend starting the migration, then walking away for the night.
Apple's support article, How to move your content to a new Mac lays out the basics of how to make this work.
Below we've added our own tips and tricks to make the process as smooth as possible based on performing thousands of migrations over the years.
PASSWORDS & APPS
SPRING CLEAN
Once you’ve sorted your content, it’s time to schedule the migration.
We recommend breaking the migration into two phases — backup and restore.
Both phases can take up to a day to complete, and you’ll retain full use of your Mac during the process.
ALTERNATIVE METHOD (If you can spare a lot of downtime).
The alternative to a two-phase backup and restore is to use Migration Assistant and migrate directly from the old Mac to the new Mac. This can also work, however, beware ... you will not have access to either Mac during this process. And remember, in our experience, Migration Assistant doesn't do a very good job of estimating how long the migration will take. Sometimes it can get stuck and never finish.
Make a Time Machine backup using any available external hard drive that has enough storage to contain your current hard drive.
Reach out to your support team for assistance in turning on Time Machine if you haven’t gone through this process before, or watch this video.
HELPFUL TIPS: If you're not in a hurry, just let Time Machine do its thing. It will take several hours — maybe even several days.
However, if you want the backup to complete more quickly, then give Time Machine full power:
sudo sysctl debug.lowpri_throttle_enabled=0
sudo sysctl debug.lowpri_throttle_enabled=1
PHASE TWO: Restore the Time Machine Backup
Set aside time to restore your Time Machine backup to your new Mac. Plan on at least 4 hours of restore time. It could take longer, it could take less. We recommend not watching it. :)
However, we do recommend watching this video if you want more details.
In our experience, it's better to reinstall applications rather than migrate them so we recommend you uncheck and NOT migrate any Applications.
Once the migration is complete, you can begin using your new destination computer. Log in and test everything — email, file sharing access, your documents, etc. Only when you're satisfied that everything is working on your new Mac, can the old Mac — and your Time Machine backup — be erased or recycled.