This is a series of tips that cover Mac OS X client edition. Server forums cover Mac OS X server on the community.

1. MacOS Catalina; macOS Mojave; macOS High Sierra; macOS Sierra; OS X El Capitan; OS X Yosemite; OS X Mavericks; OS X Mountain Lion; Mac OS X v10.7 Lion; Mac OS X v10.6 Snow Leopard; Mac OS X v10.5 Leopard; Mac OS X v10.4 Tiger; Mac OS X v10.3 and earlier; Mac OS X Technologies; Classic Mac OS (OS9, OS8 & System 7) Photos for Mac; QuickTime.
2. MacOS (originally named 'Mac OS X' until 2012 and then 'OS X' until 2016) is the current Mac operating system that officially succeeded the classic Mac OS in 2001. Although the system was originally marketed as simply 'version 10' of Mac OS, it has a history that is largely independent of the classic Mac OS.

The best Mac OS version is the one that your Mac is eligible to upgrade to. In 2021 it is macOS Big Sur. However, for users that need to run 32-bit apps on Mac, the best macOS is Mojave. Also, older Macs would benefit if upgraded at least to macOS Sierra for which Apple still releases security patches. How to Tell Which macOS You Are Running.

Here is the series of tips for related Macs. 10.6,10.7, 10.8, 10.9, 10.10,10.11,

10.12 ,10.13, 10.14 Mojave, 10.15 Catalina , 11.0 Big Sur.

See special note about resetting the SMC during updates and upgrades, later in the tip.

is an article I wrote that everyone updating their Mac should read. No update should be ventured into with operating systems or software without first ensuring your data is backed up in two separate places. Slowing down of your Mac should not lead you to assume an update will fix everything. First isolate why your Mac is slowing down or crashing before installing anything new.

Apple includes many full upgrade installer links on https://support.apple.com/en-us/HT211683

Note: APFS came about with High Sierra, and Mojave continues the practice of auto-reformatting drives into APFS that are solid state like flash drives from HFS Journaled. If you need to downgrade to an older system than High Sierra, you will need to reformat the drive again, or leave a partition with the old formatting available.

Apple released for 10.14.6 users, 2020-003 Mojave security update. If running an earlier version of 10.14, run the 10.14.6 Combo update first.

Apple recommends you have these Macs according to: https://support.apple.com/kb/SP777?locale=en_US

• MacBook (Early 2015 or newer) [model identifier 8,1 or later]
• MacBook Air (Mid 2012 or newer) [model identifier 5,1 or later]
• MacBook Pro (Mid 2012 or newer) [model identifier 9,1 or later]
• Mac mini (Late 2012 or newer) [model identifier 6,1 or later]
• iMac (Late 2012 or newer) [model identifier 12,1 or later]
• Mac Pro (Late 2013; Mid 2010 and Mid 2012 models with recommended Metal-capable graphics cards) [model identifier 5,1 or later]

bracketed items in quotes were added for additional identification purposes. Your Apple menu -> About This Mac -> System Report or System Profiler gives you the model identifier.

All of the Macs that are older than 10.11, need to be updated to 10.11 first before installing Mojave.

The oldest MacBook Air, Mac mini, and iMac which can upgrade to Mojave shipped with 10.8, Mountain Lion.

The oldest MacBook Pro which can upgrade to Mojave shipped with 10.7, Lion.

The oldest MacBook had Mac OS X 10.10 installed.

The oldest Mac Pro on the list above with the compatible graphics cards, had 10.6 originally installed, and is the only Mac that shipped with 10.6 that can install Mojave. Before upgrading to 10.7 or later, read this tip as Apple has not reintroduced a series of software that made older Mac compatible software compatible with Intel Macs since 10.6.8's release.

Apple released Mojave on September 24, 2018. Reports from:

earlier than that date were made with pre-release Mojave versions and can not be relied upon.

September 30, 2018 driver additions from third party update pages:

HP, and Samsung (HP has become the download site for at least some Mojave Samsung printers, if you have Samsung see if any are Catalina compatible)

How To Downgrade Macos Catalina To Mojave

Silverfast.

10.14.3 was released January 22, 2019. Note, some users are reporting 10.14.3 will not successfully apply as an update without an SMC reset as described how to do in this link: https://support.apple.com/en-us/HT201295

Frequently both updates and upgrades will require multiple reboots to successfully apply. Do NOT become impatient if you find the screen go blank during the update or upgrade process. If you press the power button to shut it down while it is rebooting for the update or upgrade, it may quit the process, and leave you stuck.

Mac Os Catalina To Mojave

Use the macOS Mojave forum for operating system specific questions of other end users such as yourself.

Note: https://support.apple.com/guide/disk-utility/partition-a-physical-disk-dskutl14027/mac

are directions for creating a separate partition that will allow you to dual boot into an older operating system

if you find something not compatible with the current. Once you install the older operating system, you can use the Startup manager to dual boot to the older system.

You can't install Mojave from the Finder, unless you are running 10.13.6 or earlier.

The direct download link for Mojave is:

Note: some people have had trouble downloading the latest Mojave links. https://brave.com/ has been found to be a better web browser than some if you run into issues and is known to work on Mac OS X 10.10 and later.

Note: the 2020-004 security update for Mojave has a bug with the screen saver getting stuck. To repair delays in the screen saver, 'The workaround is to choose a non-picture screen saver such as Flurry, Message, etc.' (special thanks to community member dialabrain for this report.

Is your Mac up to date with the latest version of the Mac operating system? Is it using the version required by some product that you want to use with your Mac? Which versions are earlier (older) or later (newer, more recent)? To find out, learn which version is installed now.

If your macOS isn't up to date, you may be able to update to a later version.

Which macOS version is installed?

From the Apple menu  in the corner of your screen, choose About This Mac. You should see the macOS name, such as macOS Big Sur, followed by its version number. If you need to know the build number as well, click the version number to see it.

Which macOS version is the latest?

These are all Mac operating systems, starting with the most recent. When a major new macOS is released, it gets a new name, such as macOS Big Sur. As updates that change the macOS version number become available, this article is updated to show the latest version of that macOS.

If your Mac is using an earlier version of any Mac operating system, you should install the latest Apple software updates, which can include important security updates and updates for the apps that are installed by macOS, such as Safari, Books, Messages, Mail, Music, Calendar, and Photos.