Start up from macOS Recovery

That way of downloading Mac OS X updates and new apps was introduced with Snow Leopard and means that anyone with a Mac running Mac OS X 10.5 Leopard or earlier can’t actually access the Mac App. MacOS High Sierra won’t install. If the download completes successfully but the installation doesn’t finish, force quit the installer using the same procedure as above. Restart your Mac; Launch the App Store app and go to the Purchases tab. Find macOS High Sierra and click Install.

Mac OS X Mountain Lion (version 10.8) is the nineth major release of Mac OS X (now named macOS), Apple’s desktop and server operating system for Macintosh computers. OS X Mountain Lion brings a lot of great things from iPhone, iPad, and iPod touch to the Mac. You can send iMessages. Get your Mac in on Game Center. Receive notifications.
The new Mac operating system offers more than a name change. MacOS Sierra version 10.12 moves Apple's desktop OS closer to its mobile counterpart, gaining Siri, Apple Pay, and more.
Black Friday M1 Mac deals: $899 MacBook Air, $639 Mac mini, $1,199 new MacBook Pro Special discounts on Apple's brand new Macs deliver up to $100 in savings on the Late 2020 hardware.

Determine whether you're using a Mac with Apple silicon, then follow the appropriate steps:

Apple silicon: Turn on your Mac and continue to press and hold the power button until you see the startup options window, which includes a gear icon labeled Options. Select Options, then click Continue.
Intel processor: Make sure that your Mac has a connection to the internet. Then turn on your Mac and immediately press and hold Command (⌘)-R until you see an Apple logo or other image.

If you're asked to select a user you know the password for, select the user, click Next, then enter their administrator password.

Reinstall macOS

Select Reinstall macOS from the utilities window in macOS Recovery, then click Continue and follow the installer's instructions.

Follow these guidelines during installation:

Allow installation to complete without putting your Mac to sleep or closing its lid. Your Mac might restart and show a progress bar several times, and the screen might be empty for minutes at a time.
If the installer asks to unlock your disk, enter the password you use to log in to your Mac.
If the installer doesn't see your disk, or it says that it can't install on your computer or volume, you might need to erase your disk first.
If the installer is for a different version of macOS than you expected, learn about other installation options, below.
If the installer offers you the choice between installing on Macintosh HD or Macintosh HD - Data, choose Macintosh HD.

After installation is complete, your Mac might restart to a setup assistant. If you're selling, trading in, or giving away your Mac, press Command-Q to quit the assistant without completing setup. Then click Shut Down. When the new owner starts up the Mac, they can use their own information to complete setup.

Other macOS installation options

By default, macOS Recovery installs the latest macOS that was previously installed on your Mac.* You can get other macOS versions using one of these methods:

On an Intel-based Mac, you can use Option-Command-R at startup to upgrade to the latest macOS that is compatible with your Mac. Exceptions:
- If macOS Sierra 10.12.4 or later was never previously installed, you will receive the macOS that came with your Mac, or the closest version still available.
- If your Mac has the Apple T2 Security Chip and you never installed a macOS update, you will receive the latest macOS that was installed on your Mac.
On an Intel-based Mac that previously used macOS Sierra 10.12.4 or later, you can use Shift-Option-Command-R at startup to install the macOS that came with your Mac, or the closest version still available.
Reinstall macOS from the App Store instead of using macOS Recovery. If you can't install the latest macOS, you might be able to install an earlier macOS.
Create a bootable installer, then use it to install macOS on your Mac or another Mac.

* If you just had your Mac logic board replaced during a repair, macOS Recovery might offer only the latest macOS compatible with your Mac. If you erased your entire disk instead of just the startup volume on that disk, macOS Recovery might offer only the macOS that came with your Mac, or the closest version still available.

macOS Big Sur elevates the most advanced desktop operating system in the world to a new level of power and beauty. Experience Mac to the fullest with a refined new design. Enjoy the biggest Safari update ever. Discover new features for Maps and Messages. Get even more transparency around your privacy.

Chances are, your Mac can run macOS Big Sur

The following models are supported:

MacBook (2015 or later)
MacBook Air (2013 or later)
MacBook Pro (Late 2013 or later)
Mac mini (2014 or later)
iMac (2014 or later)
iMac Pro (2017 or later)
Mac Pro (2013 or later)

To see which model you have, click the Apple icon in your menu bar and choose About This Mac.

Make sure you’re ready to upgrade.

Before you upgrade, we recommend that you back up your Mac. If your Mac is running OS X Mavericks 10.9 or later, you can upgrade directly to macOS Big Sur. You’ll need the following:

OS X 10.9 or later
4GB of memory
35.5GB available storage on macOS Sierra or later*
Some features require an Apple ID; terms apply.
Some features require a compatible internet service provider; fees may apply.

Upgrading is free and easy

Upgrading from macOS Catalina 10.15 or Mojave 10.14?

Go to Software Update in System Preferences to find macOS Big Sur. Click Upgrade Now and follow the onscreen instructions.

Upgrading from an older version of macOS?

If you’re running any release from macOS 10.13 to 10.9, you can upgrade to macOS Big Sur from the App Store. If you’re running Mountain Lion 10.8, you will need to upgrade to El Capitan 10.11 first.

If you don’t have broadband access, you can upgrade your Mac at any Apple Store.

OS X 10.9 or later
4GB of memory
35.5GB available storage on macOS Sierra or later*

Some features require an Apple ID; terms apply.
Some features require a compatible internet service provider; fees may apply.

For details about your Mac model, click the Apple icon at the top left of your screen and choose About This Mac. These Mac models are compatible with macOS Big Sur:

MacBook (2015 or later)
MacBook Air (2013 or later)
MacBook Pro (Late 2013 or later)
Mac mini (2014 or later)

iMac (2014 or later)
iMac Pro (2017 or later)
Mac Pro (2013 or later)

Siri

Requires a broadband internet connection and microphone (built-in or external).

Hey Siri

Supported by the following Mac models:

MacBook Pro (2018 or later)
MacBook Air (2018 or later)
iMac Pro (2017 or later)

Dictation, Voice Control, and Voice Memos

Requires a microphone (built-in or external).

Spotlight Suggestions

Requires a broadband internet connection.

Gestures

Mac Os Sierra Won't Download On Macbook Pro Under Any Accounting Software

Requires a Multi-Touch trackpad, Force Touch trackpad, Magic Trackpad, or Magic Mouse.

Force Touch gestures require a Force Touch trackpad.

VoiceOver gestures require a Multi-Touch trackpad, Force Touch trackpad, or Magic Trackpad.

Photo Booth

Requires a FaceTime or iSight camera (built-in or external) or USB video class (UVC) camera.

FaceTime

Audio calls require a microphone (built-in or external) and broadband intern