: Sign in with your Apple ID and scroll through your history.

If you have ever "purchased" (even for free) Mavericks in the past using your Apple ID, it is still available to you.

If you already have a version of 10.9 installed and just need to reach the final stable version (10.9.5), Apple still hosts standalone . where can I download OS X Mavericks 10.9 Update

: Launch the Mac App Store on an older Mac running a compatible OS.

Downloading OS X 10.9 Mavericks today can be a bit of a treasure hunt. Unlike newer versions of macOS, Apple has largely phased out Mavericks from its public-facing download pages. However, if you need it for a legacy machine or a specific software environment, there are still a few official (and semi-official) ways to get it.