Note: To install or upgrade other versions of OS X,see ARCHIVED: How do I install OS X 10.9 (Mavericks)?, ARCHIVED: How do I install OS X 10.8 (Mountain Lion)?, orARCHIVED: How do I install OS X 10.7 (Lion)?

Before attempting to install or upgrade Mac OS X, verify that yourcomputer meets the minimum system requirements. Then, continue yourinstallation or upgrade.

Upgrading from OS X Snow Leopard. If you’re running Snow Leopard (10.6.8) and your Mac supports macOS Sierra, you will need to upgrade to El Capitan from the App Store first. Then you can update to Sierra. Upgrading from OS X Leopard. If you’re running Leopard and would like to upgrade to macOS Sierra, first you’ll need to upgrade to OS X. Snow Leopard is the gateway to update your Mac to a newer operating system via Apple Purchases. Having seen the negative reviews, I thought I'd give it a go and see what happens. Nothing to lose. Well, imagine my surprise when I copied the iso to a USB stick, stuck it into my 2008 MacBook Pro and it worked beautifully. After resisting the Snow Leopard upgrade for nearly a year mainly due to initial reviews on the various glitches, I figured Apple has fixed all the initial woes of Snow Leopard and decided to take the plunge. I figured at $28, the upgrade is not shabby even if it is evolutionary, not revolutionary. Here is my upgrading experience.

Install Snow Leopard while keeping files,applications, and settings

If you follow these steps, the installer will replace your operatingsystem if one is already present, but will preserve your accountinformation and personal files. You may have to reinstall someapplications, however.

1. Insert the install disc (or the first install disc if you havemore than one) into your disc drive. Restart your computer whileholding down the c key. This causes yourcomputer to start up from the install disc rather than your harddrive. When you see the gray Apple insignia, releasec.
2. The Mac OS X installer should open automatically. Follow theon-screen prompts to read and accept the license agreement and beginthe installation. When prompted to choose a destination disk, selectyour preferred location and click Install.
3. When the Mac OS X installation finishes with the disc, restartyour computer. After the installation completes, a configurationprogram may begin automatically if you are installing for the firsttime. You will need to supply basic setup information for yourcomputer.
4. Update your system software to ensure that you have the mostrecent operating system components. From the Apple menu, selectSoftware Update..., and then follow the instructions onthe screen. Often, you will have to restart your computer, and you mayhave to run Software Update multiple times before it can completelyupdate your system.

Install Snow Leopard while erasing everything onyour computer

Snow Leopard Upgrade

If you follow these steps, everything that's currently on yourcomputer will be erased, and a new version of Snow Leopard installed.Make sure you've backed up your documents, music, pictures, movies,and other personal files before you proceed.

Buy Snow Leopard Upgrade

1. Insert the install disc (or the first install disc if you havemore than one) into your disc drive. Restart your computer whileholding down the c key. This causes yourcomputer to start up from the install disc rather than your harddrive. When you see the gray Apple insignia, releasec.
2. Choose your preferred language if prompted, and the Mac OS Xinstaller should open automatically. From the Utilities menu,select Disk Utility....
3. In Disk Utility, click your hard disk in the left column, and thenclick the Erase tab. Next to 'Format:', make sure Mac OSExtended (Journaled) is selected, and then give your disk a namenext to 'Name:'. If you would like to securely erase your data, clickSecurity Options..., click your preferred option, andclick OK. When you're ready, click Erase...,and then Erase again to erase your disk. Once it'scompleted, quit Disk Utility to return to the installer.
4. Back in the installer, click Continue, read and acceptthe license agreement, and begin the installation. When prompted tochoose a destination disk, select your preferred location, and theninstall.
5. When the Mac OS X installation finishes with the disc, restartyour computer. After the installation completes, a configurationprogram may begin automatically if you are installing for the firsttime. You will need to supply basic setup information for yourcomputer.
6. Update your system software to ensure you have the most recentoperating system components. From the Apple menu, select SoftwareUpdate..., and then follow the instructions on thescreen. Often, you will have to restart your computer, and you mayhave to run Software Update multiple times before it can completelyupdate your system.