Can I migrate between Macs running different versions of Mac OS? (Mojave to Catalina)

[Phrasikleia]

I have a very slow internet connection at the moment, and I'm very short on time, so I don't want to upgrade my old MacBook Pro that is running Mojave to Catalina if that's not necessary for migrating to the new MBP (which is arriving today). If I want to use migration assistant, do I need to have both machines running Catalina?

 

[CoastalOR]

You do not need to have both computers on the same OS to use Migration Assistant since it does not migrate the macOS. Per the linked Apple support instructions, "Use Migration Assistant to copy all of your documents, apps, user accounts, and settings to a new Mac from another computer." The biggest caution is to not have an account on the new Mac the same name as on the old Mac prior to migration.
https://support.apple.com/en-us/HT204350

 

[Fishrrman]

Fishrrman's "you can do it!" routine for migrating to a new Mac:

If you follow my instructions below, I guarantee a success rate of 98%:
PRINT OUT these instructions and check them off as you go along.

1. BEFORE you do anything else, run a "final" backup on your old Mac. Use an external drive for this. It can be either TM or a cloned backup using CarbonCopyCloner or SuperDuper. I prefer CCC.
I STRONGLY RECOMMEND THAT YOU DO NOT USE TM AS YOUR "MIGRATION EXTERNAL DRIVE". INSTEAD, USE EITHER CCC OR SD. Things will go better this way!
2. Shut down the old Mac and disconnect the external drive
3. Take the new Mac out of the box and set it up on the table. DO NOT PRESS THE POWER ON BUTTON until step 8 (read on). You don't want to begin setup until "the right moment".
4. If you're using an external display, connect the display using the usb-c/VGA adapter/cable that you have
5. Connect the keyboard and mouse if you use them. I STRONGLY SUGGEST that you connect them DIRECTLY to the Mac.
6. If you use a hub, leave it DISCONNECTED for now
7. Connect your backup drive -- use a usb-c adapter if needed.

OK, we're ready-to-go, so let's get goin':
8. Press the power on button for the first time.
9. The new Mac may ask for help "finding" the keyboard, just follow instructions.
10. Begin setup. At the appropriate moment, setup assistant will ask if you wish to migrate from another Mac or drive. YES, you want to do this.
11. "Aim" setup assistant at the external backup. Setup assistant will need a little time to "digest it all". BE PATIENT and give setup assistant the time it needs.
12. You will now see a list of things that can be migrated, such as applications, accounts, settings and data.
13. I suggest that you select ALL of them.
14. Let setup assistant "do its thing". It's going to TAKE A WHILE to move things over. Again, be patient. If you have a lot "of stuff", it will take a lot of time!
15. When done, you should see the login screen. Go ahead and login.
16. Once logged in, things should look pretty much as they looked on your old Mac.
17. You should check all your apps. Some may not run, and may require upgrading.
18. You can set aside the old backup, or ... "repurpose it" to become the backup for the new Mac. I'd keep the old one around for a week or so, at least.

 

[Phrasikleia]

Thanks so much for the helpful (and correct) replies. I was able to get the new MBP setup through migration assistant without having to upgrade the old one to Catalina. I didn't see Fishrrman's reply until just now and therefore did not follow much of that advice, but fortunately, everything seems to have worked out alright.

FWIW, with regards to #3 above, the new Mac powered itself on as soon as I removed the paper from the screen (or perhaps when I lifted the lid).

 

[Howard Brazee]

Fishrrman's "you can do it!" routine for migrating to a new Mac:

If you follow my instructions below, I guarantee a success rate of 98%:
PRINT OUT these instructions and check them off as you go along.

1. BEFORE you do anything else, run a "final" backup on your old Mac. Use an external drive for this. It can be either TM or a cloned backup using CarbonCopyCloner or SuperDuper. I prefer CCC.
I STRONGLY RECOMMEND THAT YOU DO NOT USE TM AS YOUR "MIGRATION EXTERNAL DRIVE". INSTEAD, USE EITHER CCC OR SD. Things will go better this way!
2. Shut down the old Mac and disconnect the external drive
3. Take the new Mac out of the box and set it up on the table. DO NOT PRESS THE POWER ON BUTTON until step 8 (read on). You don't want to begin setup until "the right moment".
4. If you're using an external display, connect the display using the usb-c/VGA adapter/cable that you have
5. Connect the keyboard and mouse if you use them. I STRONGLY SUGGEST that you connect them DIRECTLY to the Mac.
6. If you use a hub, leave it DISCONNECTED for now
7. Connect your backup drive -- use a usb-c adapter if needed.

OK, we're ready-to-go, so let's get goin':
8. Press the power on button for the first time.
9. The new Mac may ask for help "finding" the keyboard, just follow instructions.
10. Begin setup. At the appropriate moment, setup assistant will ask if you wish to migrate from another Mac or drive. YES, you want to do this.
11. "Aim" setup assistant at the external backup. Setup assistant will need a little time to "digest it all". BE PATIENT and give setup assistant the time it needs.
12. You will now see a list of things that can be migrated, such as applications, accounts, settings and data.
13. I suggest that you select ALL of them.
14. Let setup assistant "do its thing". It's going to TAKE A WHILE to move things over. Again, be patient. If you have a lot "of stuff", it will take a lot of time!
15. When done, you should see the login screen. Go ahead and login.
16. Once logged in, things should look pretty much as they looked on your old Mac.
17. You should check all your apps. Some may not run, and may require upgrading.
18. You can set aside the old backup, or ... "repurpose it" to become the backup for the new Mac. I'd keep the old one around for a week or so, at least.

I'm curious about your strong recommendation. What kinds of problems do people have when people migrate from Time Machine that they don't have from CarbonCopyCloner? I don't want to buy a 2nd backup drive, should I use my Time Machine drive for CCC until the migration is done then go back to TM?

Also, I was thinking of migrating directly from my late 2013 27" Catalina iMac to my ordered M1 24" iMac via ethernet cable (my old computer has Thunderbolt-1 and I can't find my converter). What are the upsides and downsides to doing this?

 

[Fishrrman]

I recommend CCC because I believe the process will "go faster".

You can also use an ethernet cable to connect the Macs for a migration.
However, it could impact the speed.