The official release date of Sierra was September 20, 2016. Note, it no longer has 'X' in the official name.
Macs that shipped with Sierra can be updated directly to Mojave from the Mac App Store.
10.12 is available again! https://itunes.apple.com/us/app/macos-sierra/id1127487414?ls=1&mt=12
High Sierra is also still available as of September 30, 2018. The only exception is that High Sierra needs a minimum of 10.8 installed, and will reformat SSD and and Flash drives to APFS rendering it invisible to Sierra and older systems.
Sierra can be upgraded from 10.7.5 directly if all its associated updates have been installed. Any version of 10.7 can be upgraded in this sequence before installing newer operating systems if the hardware is supported:
1. 10.7.5 Combo
Some Macs may not be able to take Sierra, but can take 10.11 and came with 10.6.8 or earlier. Apple has provided an update to 10.11 for these Macs while leaving 10.10 and 10.9 off the App Store as discussed here.
Not all 10.6.8 compatible Macs are compatible with 10.11 either.
See this tip to find out if your Mac can install Sierra from a system as old as 10.6:
As always, http://roaringapps.com/apps is an excellent third party resource to find and contribute compatibility of Mac Software. Some reports may predate the September 20, 2016 date, and should be verified with the software publisher.
Note, download times may be longer than usual on first release. Backup (link explains how) your data before you install anything.
Apple had kept the same minimum hardware requirements for Mac OS X 10.8 through 10.11.
Here are the new requirements with the Machine ID (x,x) as stated in the System Profiler for Mac OS 10.12 Sierra
- MacBook (Late 2009 or newer) 6,1
- MacBook Pro (Mid 2010 or newer) 6,1
- MacBook Air (Late 2010 or newer) 3,1
- Mac mini (Mid 2010 or newer) 4,1
- iMac (Late 2009 or newer) 10,1
- Mac Pro (Mid 2010 or newer) 5,1
This information is available on http://www.apple.com/macos/how-to-upgrade/#hardware-requirements
Apple has printer support on this knowledgebase article.
Mac OS Sierra 10.12.1, 10.12.2, 10.12.3, 10,12.4, 10.12.5, 10.12.6 are available for it as well. And as with any install should be preceded with a backup using the aforementioned backup directions.
Sierra supports new RAW formats for digital photography:
New USB serial drivers for Sierra have been made available by third party here:
A security update was released on July 9, 2018:
Safari 12 was released on September 17th for both Sierra and High Sierra through the App Store.
Unsupported Macs may have Sierra installed from the patch by http://dosdude1.com/sierrapatch.html
Use at your own risk.