“The web browser engine used by Safari, Mail, App Store and many other apps on macOS/iOS/Linux.”
WebKit describes itself to be a project with a focus on standards-based technology such as HTML, CSS and JavaScript. It’s an open source project and thus you can contribute to do. It intends to be compatible with applications, stable and performative.
Their website states clearly that the project is not a browser, science project, a bundle of reusable code or a solution to every problem.
So what is it?
It’s an engine and an engineering project.
Sometimes you may notice in CSS styles things like -webkit-border-before. Usually webkit styles will have -webkit before them.
To view the MDN docs on WebKit CSS extensions click here.
To view feature and CSS statuses click here.
WebKit does a good job when it comes to documentation. For example posts on breakpoints are clear and show users exactly how to use them within webkit.
Click here to view the full docs.