macOS Sierra was first released as a public bet in July of 2016. The operating system went golden and had its full release on September 20, 2016. Along with giving the operating system a new name, Apple is adding a lot of new features to macOS Sierra. This isn't just a simple update or a bunch of security and bug fixes.

Instead, macOS Sierra will add brand new features to the operating system, including the incorporation of Siri, expansion of Bluetooth and Wi-Fi based connectivity features, and a whole new file system that will replace the venerable but quite outdated HFS+ system that Macs have been using for the last 30 years.

When an operating system encompasses such a wide range of new features and capabilities there's bound to be a few gotcha’s; in this case, the list of Macs that will support macOS Sierra will be trimmed back by quite a bit. This is the first time in five years that Apple has removed Mac models from the list of supported devices for a Mac OS.

The last time Apple dropped Mac models from the supported list was when OS X Lion was introduced. It required Macs to have a 64-bit processor, which left the original Intel Macs off the list.

Mac Support List
The following Macs are capable of running macOS Sierra:

Macs Compatible with macOS Sierra
Mac Models Year Model ID
MacBook Late 2009 and later MacBook6,1 and later
MacBook Air 2010 and later MacBookAir3,1 and later
MacBook Pro 2010 and later MacBookPro 6,1 and later
iMac Late 2009 and later iMac10,1 and later
Mac mini 2010 and later Macmini4,1and later
Mac Pro 2010 and later MacPro5,1 and later
Aside from two late 2009 Mac models (MacBook and iMac), all Macs older than 2010 aren't able to run macOS Sierra. What isn't clear is why certain models made the cut and others didn't. As an example, a 2009 Mac Pro (not supported) has much better specs than the 2009 Mac mini that is supported.

Some have speculated that the cut-off is based on the GPU used, yet the late 2009 Mac mini and MacBook only had an NVIDIA GeForce 9400M GPU that was pretty basic, even for 2009, so I don’t think the limitation is the GPU.

Likewise, the processors in the two late 2009 Mac models (Intel Core 2 Duo) are pretty basic when compared to a 2009 Mac Pro’s Xeon 3500 or 5500 series processors.

So, while people speculate that the issue is with CPUs or GPUs, I’m not inclined to think that's the reason. I’m more inclined to believe it’s the presence of a peripheral control on Mac’s motherboards that is being used by macOS Sierra for some basic function. Perhaps it's needed to support the new file system or one of the other new features of Sierra that Apple didn't want to go without.

Apple’s not saying why the older Macs didn't make the support list, but I’m guessing that after MacOS Sierra is fully released, there may be methods found to get a few of the old Macs working with the new OS. If that should happen, I’ll add a list of working but not supported Macs for the new OS.

Update: As expected a macOS Sierra Patch Tool has been created that will allow some previously unsupported Macs to work with macOS Sierra. The process is a bit long winded, and frankly not something I would bother with on any of my old Macs. But if you must have macOS Sierra on an unsupported Mac, here are the instructions: macOS Sierra Patcher Tool for Unsupported Macs.

Be sure and have a recent backup before proceeding with the patch and install process outlined at the above link.

Beyond the Basics
Apple hasn't yet issued specific minimum requirements beyond the list of supported Macs. By going through the support list, and looking at what a base install of the macOS Sierra preview needs, I’ve come up with these macOS Sierra minimum requirements, as well as a list of preferred requirements.

Memory Requirements
Item Minimum Recommended Much Better
RAM 4 GB 8 GB 16 GB
Drive Space * 16 GB 32 GB 64 GB
* Drive space size is an indication of the amount of free space needed just for the OS install and does not represent the total amount of free space that should be present for effective operation of your Mac.

Be sure to check out our How Much Free Drive Space Do I Need article.