How to migrate essential information from a 2020 iMac to a 512GB Mini M4, excluding large files and folders?

How to transfer only the esential information during migration from a 2020 iMac to a 512gb Mini M4

I bought a new 512gb M4 and am having a real problem trying to migrate the essential info from my 2020 iMac (2tb fusion). I have a 2TB Samsung T7 SSD where I've managed to Time Machine down to 525gb but I can't seem to reduce that any further even when I've excluded all I could think of (pics, musoc, download folder) except the apps and library. When I look at the size of the back up it shows 525gb but when I check the size of all the folders there seems to be an invisible 300gb's hidden somewhere. It's driving me nuts!

I just want to transfer my apps and all my settings, passwords etc but the migration won't let me.

[Re-Titled by Moderator]

Original Title: Cannot migrate

Mac mini (M4, 2024)

Posted on Nov 22, 2025 6:56 PM

21 replies

Nov 24, 2025 8:09 AM in response to media_lush

Get the 2TB option, you can't fit all of your 2TB files in 512 GB, return the Mac mini and buy a new one with a minimum 2TB storage

Nov 24, 2025 10:29 AM in response to Cheekooking123

That's an awful suggestion unless the OP has Musk's financial resources.

2TB will cost an extra £800 and you can get the same to plug in for £100.

media_lush Author

Level 1

59 points

Nov 24, 2025 8:22 PM in response to Matti Haveri

I've decided to go the 'buy a 3rd party 2TB chip route'😬 - (I've answered in more detail elswhere in this thread).

media_lush Author

Level 1

59 points

Nov 24, 2025 8:27 PM in response to Servant of Cats

what I actually wrote:

"the thing is I was on 49gb or so and attempted to get rid of a few files with no success and I have no idea why double that amount is showing up"

Old Toad

Level 10

215,196 points

Nov 24, 2025 11:23 AM in response to media_lush

Here's how I would do it:

1 - get an external SSD (I recommend OWC, MacSales.com).

2 - format it APFS with Disk Utility.

3 - copy the Pictures, Music and Movies folders to it from your 2020 iMac.

4 - make sure the Photos, Music and Movies libraries work as expected from the external SSD.

5 - see if that will get you down below 512 GB on your 2020 iMac, preferably to about 400 GB.

6 - if you still need to clear more space create a Documents folder on the external SSD and copy enough files from the Documents folder on your 2020 iMac, delete them from your 2020 iMac to get down to around 400 GB.

7 - delete the contents of the Pictures, Music and Movies folders but NOT the folders them selves.

8 - when you get down to the loser size make a Time Machine backup of your 2020 iMac.

9 - connect your Time Machine drive to the new Mac Mini, boot up the Mini and use Migration Assistant to migrate all of your user data and other options to the new Mini when you get to that stage of the process.

10 - rename the Pictures, Music, Movies an Documents folder to Pictures-2, Music-2, etc.

11- remove those folders from the Finder's sidebar and add the -2 folders to it.

NOTE: if you don't need to copy the Movies folder or documents to the external SSD to reach the size goal then don't.

What 400GB? Because it wise to keep about 80-100GB free to facilitate optimal system and application performance.

Nov 26, 2025 2:28 AM in response to media_lush

If you haven't already bought an internal SSD just get a 2TB NVMe with either a USB-C or Thunderbolt enclosure and boot from that as I detailed earlier.

It solves all your problems dead easily at minimal cost.

The only downside is that Apple AI and Apple Pay are not available but if you did require them you could simply boot into the internal SSD . . . it takes less than a minute.

How to migrate essential information from a 2020 iMac to a 512GB Mini M4, excluding large files and folders?