ISO/IEC 19775, Extensible 3D (X3D), defines a system that integrates 3D graphics and multimedia. Conceptually, each X3D file is a 3D time-based space that contains graphic and aural objects that can be dynamically modified through a variety of mechanisms. This part of ISO/IEC 19776 defines a mapping of the abstract objects in X3D to a specific X3D encoding written out in a compact binary form.

Each X3D file encoded using the Compressed binary encoding:

1. supports all of the purposes of X3D files defined in the X3D abstract specification ISO/IEC 19775;
2. encodes X3D constructs in a compressed binary format, taking advantage of geometric and information-theoretic compression techniques.

X3D files encoded using the Compressed binary encoding may be referenced from files using other X3D encodings, and may itself reference other X3D files encoded using other X3D encodings. Sets of X3D files that use multiple encodings can only be processed by browsers that support all of the utilized X3D encodings.