https://dom.spec.whatwg.org/ is the only DOM spec now being actively maintained—the one that implementors are actually working from and the only one that’s incorporating new features and receiving bug fixes. (https://www.w3.org/TR/dom/ is a frozen Rec that’s not up to date with current implementations and so should not be used by implementors or web developers, and nobody is working on WD to replace it.)
https://dom.spec.whatwg.org/ is the only DOM spec now being actively maintained—the one that implementors are actually working from and the only one that’s incorporating new features and receiving bug fixes. (https://www.w3.org/TR/dom/ is a frozen Rec that’s not up to date with current implementations and so should not be used by implementors or web developers, and nobody is working on WD to replace it.)