On OSX: After an update to El Capitan, I found that Safari 9 was installed by default. For software testing purposes, I need to test a web app through Safari 8 (which is still the latest version in Yosemite). I searched but there is no way (expect for browserstack) to install or emulate an older version of Safari.
Other than downgrading to Yosemite, is there a way to do it?
Probably the closest you could get is by downloading one of the WebKit nightlies that matches up with your desired Safari version.
Wikipedia's Safari version history article lists the corresponding WebKit version for each Safari release. If you then look up the tag for that version in the WebKit source, you can find a corresponding revision number. Finally, you can use the WebKit Nightly Archives to download the closest nightly build.
Safari 8.0.7 used WebKit version 600.7.12, which seems to most closely correspond to WebKit build r185729.
I don't know if you can run more than one WebKit build on a machine, but you could at least one older version to target, in addition to Safari.
I also searched for getting older Safari Versions and found a website which offers them for download.
They are too old for my Version of OSX so I was not able to test it - but maybe it works for someone.
来源：https://stackoverflow.com/questions/33423269/is-there-a-way-to-install-emulate-an-older-version-of-safari-i-e-8