Any source outside of Apple is suspect, and you should inquire on Apple Discussions before attempting to download such updates to determine if your update is able to be applied to your system. If the source is Apple and you can download updates to your operating system, assuming you meet the requirements given on the download page. Retail installer discs icons are included where possible, if you have an older machine that is compatible. This tip: information about when Macs no longer came with installer discs, and which ones those were with Mac OS X 10.7 or later. This article can help with determining which Intel operating system your Mac came with if it is Intel: OS X versions and builds included with Mac computers - Apple Support This article can help with determining which PowerPC operating system your Mac came with, if it is a PowerPC: Mac OS: Versions, builds included with PowerPC Macs (since 1998) - Apple Support

If you need help finding how to backup other operating systems, be sure to ask in the appropriate forum. Link for backing up only refers to Mac OS X applications.

Before you download be sure to backup your data.

In the discussion below the network refers to the internet, and the server in question is Apple's server. Some people may not be aware, but 'download' means to retrieve off a network server. For it and newer releases, please use the link to the left. This tip has not been updated High Sierra's release.

Original mac os x 10.0