OSX 10.12 is the oldest supported Mac OS; OSC Documentation has been updated. Fixed a bug where the wrong I/O was activated. Fixes related to the offline-mode. The idea is that if you have a main rig where you are connected to, lets say a USB-Interface on a mixer.

Professor Emeritus

1. Nathaniel Ostrom MSU Department: Integrative Biology, Professor Ph.D., Memorial University of Newfoundland, 1992 Biogeochemistry Email: ostromn@msu.edu.
2. Nov 29, 2017 The following method allows you to download Mac OS X Lion, Mountain Lion, and Mavericks. Start your Mac holding down Command + R. Prepare a clean external drive (at least 10 GB of storage). Within OS X Utilities, choose Reinstall OS X.

B.S., 1966, Rutgers University
Ph.D., 1971, University of Massachusetts
Post-doctoral studies: 1971-1973, University of Wisconsin

Wertz JT, Breznak JA. Physiological ecology of Stenoxybacter acetivorans, an obligate microaerophile in termite guts. Appl Environ Microbiol. 2007 Nov;73(21):6829-41.

Wertz JT, Breznak JA. Stenoxybacter acetivorans gen. nov., sp. nov., an acetate-oxidizing obligate microaerophile among diverse O2-consuming bacteria from termite guts. Appl Environ Microbiol. 2007 Nov;73(21):6819-28.

Eichorst SA, Breznak JA, Schmidt TM. Isolation and characterization of soil bacteria that define Terriglobus gen. nov., in the phylum Acidobacteria. Appl Environ Microbiol. 2007 Apr;73(8):2708-17.

Sutka RL, Ostrom NE, Ostrom PH, Breznak JA, Gandi H, Pitt AJ, Li F. Distinguishing nitrous oxide production from nitrification and denitrification on the basis of isotopomer abundances. Appl Environ Microbiol. 2006 Jan;72(1):638-44.

Graber JR, Breznak JA. Folate cross-feeding supports symbiotic homoacetogenic spirochetes. Appl Environ Microbiol. 2005 Apr;71(4):1883-9.

Stevenson BS, Eichorst SA, Wertz JT, Schmidt TM, Breznak JA. New strategies for cultivation and detection of previously uncultured microbes. Appl Environ Microbiol. 2004 Aug;70(8):4748-55.

Graber JR, Leadbetter JR, Breznak JA. Description of Treponema azotonutricium sp. nov. and Treponema primitia sp.nov., the first spirochetes isolated from termite guts. Appl Environ Microbiol. 2004 Mar; 70(3):1315-20.

Graber JR, Breznak JA. Physiology and nutrition of Treponema primitia, an H2/CO2-acetogenic spirochete from termite hindguts. Appl Environ Microbiol. 2004 Mar;70(3):1307-14.

So, you’ve decided to download an older version of Mac OS X. There are many reasons that could point you to this radical decision. To begin with, some of your apps may not be working properly (or simply crash) on newer operating systems. Also, you may have noticed your Mac’s performance went down right after the last update. Finally, if you want to run a parallel copy of Mac OS X on a virtual machine, you too will need a working installation file of an older Mac OS X. Further down we’ll explain where to get one and what problems you may face down the road.

A list of all Mac OS X versions

We’ll be repeatedly referring to these Apple OS versions below, so it’s good to know the basic macOS timeline.

STEP 1. Prepare your Mac for installation

Given your Mac isn’t new and is filled with data, you will probably need enough free space on your Mac. This includes not just space for the OS itself but also space for other applications and your user data. One more argument is that the free space on your disk translates into virtual memory so your apps have “fuel” to operate on. The chart below tells you how much free space is needed.

Note, that it is recommended that you install OS on a clean drive. Next, you will need enough disk space available, for example, to create Recovery Partition. Here are some ideas to free up space on your drive:

• Uninstall large unused apps
• Empty Trash Bin and Downloads
• Locate the biggest files on your computer:

Go to Finder > All My Files > Arrange by size
Then you can move your space hoggers onto an external drive or a cloud storage.
If you aren’t comfortable with cleaning the Mac manually, there are some nice automatic “room cleaners”. Our favorite is CleanMyMac as it’s most simple to use of all. It deletes system junk, old broken apps, and the rest of hidden junk on your drive.

Download CleanMyMac for OS 10.4 - 10.8 (free version)

Mac Os Download

Download CleanMyMac for OS 10.9 (free version)

Download CleanMyMac for OS 10.10 - 10.14 (free version)

STEP 2. Get a copy of Mac OS X download

Normally, it is assumed that updating OS is a one-way road. That’s why going back to a past Apple OS version is problematic. The main challenge is to download the OS installation file itself, because your Mac may already be running a newer version. If you succeed in downloading the OS installation, your next step is to create a bootable USB or DVD and then reinstall the OS on your computer.

How to download older Mac OS X versions via the App Store

If you once had purchased an old version of Mac OS X from the App Store, open it and go to the Purchased tab. There you’ll find all the installers you can download. However, it doesn’t always work that way. The purchased section lists only those operating systems that you had downloaded in the past. But here is the path to check it:

1. Click the App Store icon.
2. Click Purchases in the top menu.
3. Scroll down to find the preferred OS X version.
4. Click Download.

This method allows you to download Mavericks and Yosemite by logging with your Apple ID — only if you previously downloaded them from the Mac App Store.

Without App Store: Download Mac OS version as Apple Developer

If you are signed with an Apple Developer account, you can get access to products that are no longer listed on the App Store. If you desperately need a lower OS X version build, consider creating a new Developer account among other options. The membership cost is $99/year and provides a bunch of perks unavailable to ordinary users.

Nevertheless, keep in mind that if you visit developer.apple.com/downloads, you can only find 10.3-10.6 OS X operating systems there. Newer versions are not available because starting Mac OS X Snow Leopard 10.7, the App Store has become the only source of updating Apple OS versions.

Purchase an older version of Mac operating system

You can purchase a boxed or email version of past Mac OS X directly from Apple. Both will cost you around $20. For the reason of being rather antiquated, Snow Leopard and earlier Apple versions can only be installed from DVD.

Buy a boxed edition of Snow Leopard 10.6
Get an email copy of Lion 10.7
Get an email copy of Mountain Lion 10.8

The email edition comes with a special download code you can use for the Mac App Store. Note, that to install the Lion or Mountain Lion, your Mac needs to be running Snow Leopard so you can install the newer OS on top of it.

How to get macOS El Capitan download

If you are wondering if you can run El Capitan on an older Mac, rejoice as it’s possible too. But before your Mac can run El Capitan it has to be updated to OS X 10.6.8. So, here are main steps you should take:

1. Install Snow Leopard from install DVD.
2. Update to 10.6.8 using Software Update.
3. Download El Capitan here.

“I can’t download an old version of Mac OS X”

If you have a newer Mac, there is no physical option to install Mac OS versions older than your current Mac model. For instance, if your MacBook was released in 2014, don’t expect it to run any OS released prior of that time, because older Apple OS versions simply do not include hardware drivers for your Mac.

But as it often happens, workarounds are possible. There is still a chance to download the installation file if you have an access to a Mac (or virtual machine) running that operating system. For example, to get an installer for Lion, you may ask a friend who has Lion-operated Mac or, once again, set up a virtual machine running Lion. Then you will need to prepare an external drive to download the installation file using OS X Utilities.

Ostrom Mac Os Download

After you’ve completed the download, the installer should launch automatically, but you can click Cancel and copy the file you need. Below is the detailed instruction how to do it.

STEP 3. Install older OS X onto an external drive

The following method allows you to download Mac OS X Lion, Mountain Lion, and Mavericks.

1. Start your Mac holding down Command + R.
2. Prepare a clean external drive (at least 10 GB of storage).
3. Within OS X Utilities, choose Reinstall OS X.
4. Select external drive as a source.
5. Enter your Apple ID.

Now the OS should start downloading automatically onto the external drive. After the download is complete, your Mac will prompt you to do a restart, but at this point, you should completely shut it down. Now that the installation file is “captured” onto your external drive, you can reinstall the OS, this time running the file on your Mac.

1. Boot your Mac from your standard drive.
2. Connect the external drive.
3. Go to external drive > OS X Install Data.

Locate InstallESD.dmg disk image file — this is the file you need to reinstall Lion OS X. The same steps are valid for Mountain Lion and Mavericks.

How to downgrade a Mac running later macOS versions

If your Mac runs macOS Sierra 10.12 or macOS High Sierra 10.13, it is possible to revert it to the previous system if you are not satisfied with the experience. You can do it either with Time Machine or by creating a bootable USB or external drive.
Instruction to downgrade from macOS Sierra

Instruction to downgrade from macOS High Sierra

Instruction to downgrade from macOS Mojave

Instruction to downgrade from macOS Catalina

Before you do it, the best advice is to back your Mac up so your most important files stay intact. In addition to that, it makes sense to clean up your Mac from old system junk files and application leftovers. The easiest way to do it is to run CleanMyMac X on your machine (download it for free here).

Mac Os Mojave

Visit your local Apple Store to download older OS X version

Ostrom Mac Os 7

If none of the options to get older OS X worked, pay a visit to nearest local Apple Store. They should have image installations going back to OS Leopard and earlier. You can also ask their assistance to create a bootable USB drive with the installation file. So here you are. We hope this article has helped you to download an old version of Mac OS X. Below are a few more links you may find interesting.