@sparkles3020
WebKit IS NOT a browser, it is the rendering framework that makes Safari work.
Several other browsers use the WebKit renderer as well.
The builds of WebKit on webkit.org are UNTESTED NIGHTLY BUILDS of the WebKit framework, that depend on Safari in order to function.
If you are not a web developer, you should not be running the WebKit nightlies, and instead just be using Safari itself.
That said, provided you get an up to date nightly build of WebKit, it will function on El Capitan.