X3D (Extensible 3D) is an interactive 3D vector graphics format. It is the successor to VRML.
X3D is standardized in ISO/IEC 19775 (X3D), ISO/IEC 19776 (X3D encodings), and ISO/IEC 19777 (X3D language bindings).
There are three standard ways to encode an X3D file.
An XML-encoded X3D file uses extension .x3d, and MIME type model/x3d+xml. The file may be gzip-compressed, and use extension .x3dz or .x3d.gz.
A file using X3D's compressed binary encoding uses extension .x3db, and MIME type model/x3d+binary. The file may be gzip-compressed (even though the encoding name may suggest it is already compressed), and use extension .x3dbz or .x3db.gz. (.x3dbz may not be mentioned in the specification, but it is implied by the MIME type registration.)
A Classic VRML-encoded X3D file uses extension .x3dv, and MIME type model/x3d+vrml. The file may be gzip-compressed, and use extension .x3dvz or .x3dv.gz. This format is similar to VRML.
With uncompressed XML encoding, an X3D file has a line beginning with "
<!DOCTYPE X3D PUBLIC", followed by an "
<X3D>" XML element.
Classic VRML-encoded X3D files begin with text similar to "
#X3D V3.1 utf8".