Annex C ECMAScript scripting reference of Part 1 of ISO/IEC 14772 defines an ECMAScript specification to the script interface. Most of the standard objects added by this specification are interchangable. However, due to the differing capabilities of the SAI and VRML services, the Browser object definitions are not interchangeable between the two environments. This applies to all of the objects defined in ISO/IEC 14772-1 C ECMAScript scripting reference. This specification defines the interfaces that user code shall use in order to interact with an X3D scene graph.

Because the two object sets look very similar, but are not totally interchangable, when a browser finds a script that defines its content with ECMAScript, it shall determine which set of objects to support based on the declared protocol type if the script code is inlined. Scripts that require backwards compatibility shall use the protocol type "javascript:". The objects and semantics from ISO/IEC 14772-1 Annex C are to be used. In all other cases, it is assumed to be the semantics and objects defined in this part of ISO/IEC 19777.

External access to the browser shall be through the use of the objects and semantics defined in this part of ISO/IEC 19777. A conformant browser shall only support these objects and semantics when registering standard objects with the containing application's ECMAScript engine. Although part 2 of ISO/IEC14772 does not define formal bindings to the browser for ECMAScript programming, it shall be an error to support VRML objects and semantics if the browser claims conformance to this specification.