Have you noticed that once Apple releases a new version of the Mac operating system (macOS) that previous versions vanish from the App Store? Have you ever needed to reinstall one of these older versions of the Mac operating system (macOS)? It can be challenging to do this since Apple does not make older versions readily available unless you saved your own copy of the installer for the older version. I recently learned that some older versions are still available on the App Store.
This article on wphosting.tv has links for downloading some older versions of the Mac operating system (macOS). If you think you might ever need to install an older version then I recommend you download the installers now and then save the installer file so you can create your own install disk, if needed. This Apple support article currently provides instructions on how you can create your own installer disk for El Capitan, Sierra, High Sierra and Mojave. Alternatively you could use an application like DiskMaker X.
As of February 2019, Apple has links to get these versions from the App Store:
Mojave (10.14) from the App Store (No surprise here, since this is the current version of macOS)
No App Store link is provided for either El Capitan (10.11), Yosemite (10.10) or Mavericks (10.9). In fact, the article doesn’t even mention Mavericks.