[an4rchy]

It would be great if they mentioned El Capitan as a pre- requisite before people download and find out.

I know the expectation is that most Macs are up to date but if you can't install it on Yosemite, they should let people know.

[X-Istence]

It's mentioned right there on the download page:

https://developer.apple.com/safari/download/

"Compatible with OS X 10.11.4 or later"