This is the repository for the JavaScript spec. This specification used to document the differences between the ECMAScript specification and the compatibility and interoperability requirements for ECMAScript implementations in web browsers.
Nowadays its contents have been upstreamed into ECMAScript, Annex B. The remaining web compatibility issues are tracked here: https://github.com/tc39/ecma262/labels/web%20reality.
See “Sunsetting the JavaScript Standard” for more information.