macOS Sierra is Apple's latest update to its Mac desktop operating system software. It is available to download for free on the Mac App Store. In this article we explain how to download and install macOS Sierra on your Mac. We'll walk you through the install and update process, and guide you past the potential headaches and problems you may encounter.

If you'd like to find out a bit more about macOS Sierra first, read: macOS Sierra current version details and  macOS Sierra vs Mac OS X El Capitan

Before you perform any big update to your Mac you should back up your Mac and do some other housekeeping tasks. We strongly recommend you follow our tips for getting your Mac ready before you install macOS Sierra, you can read them below. [Jump to How to prepare your Mac for macOS Sierra]

At the very least you should create a back up. Luckily, Apple makes it easy to back up your Mac using Time Machine, so there is no excuse not to create a Time Machine backup before installing macOS Sierra. We have this article about how to back up your Mac using Time Machine.

How to install macOS Sierra on a Mac

Follow these instructions to install macOS Sierra, also known as macOS 10.12 on your Mac. 

  1. Once you've backed up your Mac, launch the Mac App Store (see the Mac App Store icon below) and search for macOS Sierra
  2. Click Download to initiate the download
  3. Fill out your Apple ID information if prompted
  4. Download progress will appear in your Purchases tab
  5. Once the download has finished, you'll see a macOS Sierra installer launch
  6. Follow the on-screen insturctions to finish installing the software update, which should take around half an hour depending on the spec of your Mac

If you have already installed macOS Sierra and just want to install the latest update to that software you will find it under the Mac App Store updates tab.

Reasons not to install macOS Sierra on your Mac

If you are feeling cautious about installing Sierra on your Mac because your Mac is a little long in the tooth, read: How to install macOS Sierra on older Mac

Another reason why you might not want to run Sierra on your Mac is if you have some software that you need to use that may not work in the new operating system. Luckily there are a few ways you can try out Sierra without removing an older version of OS X from your Mac, we look at these below.

How to install macOS Sierra on an external hard drive

Luckily you don't have to install the update on your Mac at all - you can install it on an external hard drive.

You'll want to use a fast drive if you can - Thunderbolt drives are comparable to the internal drives on a Mac, but if you do not have a Mac with Thunderbolt then consider using a USB 3.0 drive.

Adding a second hard drive, formatting it and installing macOS Sierra on it is the safest way to get a good look at the new operating system. It'll leave your current configuration intact and allow you to play around with Sierra.

To install Sierra on a external hard drive follow the following guide:

  1. Connect the external hard drive.
  2. Launch Disk Utility (choose Go > Utilities to find it).
  3. Select the drive in the sidebar (the root drive, not the volume it contains).
  4. Click Partition.
  5. Ensure that Partition Layout says 1 Partition.
  6. Give it a name like "macOS Sierra".
  7. Click Options and ensure that Guide Partition Table is selected. Click OK.
  8. Click Apply and Partition.

Now download the macOS Sierra installation from the Mac App Store and follow these instructions to install the beta on the hard drive:

  1. Download the macOS Sierra installer from the App Store, and open it once downloaded.
  2. Click Continue.
  3. Click Agree and Agree.
  4. Click Show All Disks.
  5. Highlight the external hard drive.
  6. Click Install.
  7. Enter your Admin password
  8. To run Sierra, open System Preferences > Startup Disk. Select the drive you wish to start up the Mac and click Restart.
  9. You can also hold down Option during startup to pick the drive you wish to use to start up the Mac.

How to dual-boot OS X El Capitan and macOS Sierra on a Mac

If you don't have a spare external hard drive (or the one you have is slower than you would like) you can partition the main hard drive into two separate drives and then install macOS Sierra on one and OS X 10.11 El Capitan on the other.

The only issue with partitioning your drive is that you will have to wipe your internal hard drive and reinstall OS X 10.11 El Capitan along with the new software.

If you want to keep any of your current work, you need to create a backup of Mac OS X 10.11 El Capitan and ensure that it will fit on your smaller partitioned drive.

To create your partition follow these instructions:

  1. Boot Mac OS X into recovery mode (Hold down Option during startup).
  2. Use Disk Utility in recovery mode to wipe the main hard drive and split it into two partitions.
  3. Use the Install option in Recovery to install OS X 10.11 El Capitan onto the main partition.
  4. Next restore the data to El Capitan from your Time Machine (or other backup).
  5. Follow the steps above to install the macOS Sierra Preview onto the second partition.

How to prepare your Mac for macOS Sierra

While Sierra should be pretty easy to install, before you perform any big update to your Mac operating system, you should complete a few tasks to ensure that your Mac is ready to go.

Here are ten things you really ought to do before OS X El Capitan launches.

1. Back up your Mac before installing

No matter what, we recommend a full back up before you install the latest version of macOS (especially if you are installing a beta, but even if you are installing the final version). Apple makes it easy to back up your Mac using Time Machine, so there is no excuse not to create a Time Machine backup before installing a new macOS.

We have this article about how to back up your Mac using Time Machine.

2. Make sure you have sufficient RAM

If your Mac is on the list of supported machines, it's likely you won't run into any problems, but it's worth checking that you also have enough RAM to run the latest version of macOS. Apple says you'll need at least 2GB RAM, although 4GB is advisable. All the supported Macs have at least 4GB RAM, and these days most Macs have 8GB as standard, some even have 16GB. If you have less than 4GB RAM it is definately time to consider upgrading to a new Mac, or installing more RAM – if you decide to do that, make sure that the RAM you choose is compatible. Read about how to update the RAM in your Mac here.

3. Make sure you have enough space for the new version of OS X

Apple suggests that you should have 8GB of free space on your Mac's drive before you install a major OS X update, but we recommend aiming for 15GB to 20GB. The Yosemite installer was 5.16GB, for example, and you'll need to allow some room for temporary files. If space is looking tight, here's an article about freeing up space on your Mac.

4. Get access to the Mac App Store

If you are still running Leopard and don't have access to the Mac App Store you really really really need to upgrade! Current versions of OS X are available only via the Mac App Store and the Mac App Store arrived in Mac OS X 10.6 Snow Leopard. Luckily you can still get hold of a copy of Snow Leopard from Apple. It costs £14.

5. Update your software for the latest version of macOS

Before you upgrade to the new version of OS X, make sure you install the latest updates to the version of OS X that you're currently running. From time to time there will be software update to improves stability, for example, and there is always a chance that you may have a problem updating to the new version of the Mac operating system if you hadn't pre installed this essential update to the previous version, so do your homework first.

To make sure you are up to date, click on the App Store icon in the Dock and select Updates. You can also click on the Apple logo at the top left of your screen and select Software Update from there.

6. Update your third party apps

Make sure you have updated any third party apps too. Those updates may include changes that are required for upgrading to the latest macOS and if you don't run the updates they may not work properly once you have updated.

To update apps you've bought from the Mac App Store, launch the App Store app and click the Updates button in the toolbar. Then click Update All, simply providing your Apple ID and password when prompted.

For apps that you purchased elsewhere you'll need to manually install updates. You can check if there are updates available from the application's menu, in Microsoft Word, for example, it's a case of clicking on Help > Check for Updates.

Check compatibility with your third party apps before updating the macOS. That way you will be up and running immediately, rather than being frustrated by your favorite apps and add-ons not working.

7. Ditch really old software

If you're still running Snow Leopard (OS X 10.6), you may still be using a few PowerPC programs - software that was never updated to run natively on Macs with Intel processors. Apple used to provided software called Rosetta that translated PowerPC code so it could run on Intel Macs. When Snow Leopard (OS X 10.6) launched Rosetta was no longer installed by default, but it was possible to download and install Rosetta if you wanted to run a PowerPC program. However, Apple killed Rosetta completely when Lion (10.7) was released, and it remains unavailable to this day.

Any PowerPC apps you have won't work when you update your system, so you'll either need to ditch them and find alternatives, or stay in the dark ages and run very old software.

To find out if any of your applications are PowerPC programs, launch Snow Leopard's System Profiler utility (in /Applications/Utilities), select Applications (under Software in the sidebar), and then click the Kind column header, which sorts the list of applications by processor type. Any programs listed as PowerPC will not work with the new operating system, they won't even work in Yosemite, Mavericks, Mountain Lion, or Lion.

8. Make sure your Mac is healthy

You should make sure that your Mac is completely healthy before installing a big update to the system.

Open Disk Utility (in /Applications/Utilities), select your startup drive from the list on the left, click the First Aid tab to the right, and then click Verify. If Disk Utility finds problems, you'll need to boot from a different volume to perform the actual repairs using the Repair Disk button.

Boot into recovery mode (by holding down Command+R at startup) and use Disk Utility from there to perform the recommended repairs.

You can also run the Apple Hardware Test (for Macs older than June 2013) or Apple Diagnostics (for Macs from June 2013 or later). Both tests check your Mac for other hardware issues, such as bad RAM.

Read more about using Disk Repair to fix a Mac here.

9. Set up iCloud

iCloud is heavily integrated into many apps and system services. Make sure you are logged into iCloud and enable syncing before you start updating and things should go smoothly.