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Downgrading from Mountain Lion to Snow Leopard?


macrumors member
Original poster
Nov 4, 2011
Hi guys,

Any one have any experience in or know if it's possible to downgrade from a newer version of OSX, like Mountain Lion, to an older version of OSX, like Snow Leopard, while being able to transfer all of your data via Time Machine and have everything work like normal?

I recall trying it once myself, but ran into all sorts of issues with non-compatibility type things, etc.

The only reason I ask is because I'd really like to downgrade my main Mac Pro back to Snow Leopard, as I'm getting all sorts of hiccups in Mountain Lion, and really don't care for the new take on OSX as of Lion, personally. I've got tons of audio files (it's a Logic workstation) in all sorts of random folders tucked away here and there, tons of VSTs and AUs it'd take ages to find and re-download, etc.
Last edited:


Apr 15, 2004
I wouldn't risk transferring data beyond stuff like documents manually. I don't think Time Machine is going to work at all.

Might just be better to wait for 10.8.1.


macrumors 68000
Sep 24, 2008
Boon Docks USA
Try installing SL on another disk, then try to pull it of the ML disk. Or, export from ML to a disk, then install SL on its own disk, then import. Wouldn't delete your ML disk until you know it works.


macrumors newbie
Aug 10, 2012


I tried also to downgrade, but failed miserably so far.
Tried this workaround:
and also the simpler one to go back using a Time Machine back-up I had from my former (stolen...) laptop.
No joy: the system seems to be locked with ML and refuse even a reformatting from the install DVD of Snow Leopard.
If you have any suggestions, I'll be glad to hear about it.
My main reason for downgrading is that I use this 'Book for my work and my data reduction software from ESO (MIDAS) will not properly compile on ML...while it was working perfectly on 10.6.8

System: MacBookPro 2.9 Ghz, 8Gb RAM.

Thanks, Emanuela


macrumors 604
Aug 10, 2010
Poole, England
This does work with Time Machine when downgrading to Lion, but I haven't tried all the way back to Snow Leopard. I would use Migration Assistant after you've done a clean install of Snow Leopard and then only tick Documents, not Applications or Settings.
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