# X3D and X3DV Files: What They Are and How to Open Them Online X3D is the ISO web 3D scene format; .x3d files use XML and .x3dv files use the classic VRML-style syntax. Learn what a CAD export in X3D contains, how to open one online and why its units need checking. X3D is a 3D scene format maintained by the Web3D Consortium and published as ISO/IEC 19775 and 19776. [Web3D X3D specifications](https://www.web3d.org/standards). It is the successor of VRML97, and the same scene can be written in more than one encoding: `.x3d` files use XML, `.x3dv` files use the ClassicVRML syntax that looks like a VRML file with an `#X3D` header. CAD systems, simulation tools and STEP-to-web pipelines export it when a model has to be shown in a browser without a CAD licence. You can open either encoding in [the CADProps workspace](https://www.cadprops.com/workspace/index.md). It reads the static scene and shows it as an approximate triangle mesh. That is enough to look at the model, check its bounding box, measure point-to-point distances and export STL, OBJ, GLB, glTF, 3MF or mesh STEP after sign-in. It is not an exact CAD solid. ## Which encoding do you have Open a copy in a text editor and read the first lines: | You see | Encoding | Extension | |---|---|---| | `` and an `` element | XML | `.x3d` | | `#X3D V3.3 utf8` (or V4.0) on the first line | ClassicVRML | `.x3dv` | | Binary bytes | Compressed binary encoding | `.x3db` (not read here) | Both text encodings may also arrive gzip-compressed under the same extension; CADProps unpacks that within its normal size limits. A file whose first line is `#VRML V2.0 utf8` is VRML97, not X3D; open it as `.wrl`, which the same workspace also reads. ## What CADProps shows from an X3D scene The reader walks the scene graph and keeps geometry that has a fixed shape: - Triangle and polygon meshes: `IndexedFaceSet`, `IndexedTriangleSet`, triangle strips and fans, with their transforms and `DEF`/`USE` instances. - Primitives: `Box`, `Sphere`, `Cylinder` and `Cone`, plus `Extrusion` and `ElevationGrid`. - CAD structure from the X3D CAD component: `CADAssembly`, `CADPart` and `CADFace` become the part tree, so you can hide parts or select one and read its bounding box. - NURBS surfaces: `NurbsPatchSurface` is tessellated for the preview. `NurbsTrimmedSurface` is cut along its trimming loops on a sampled grid, so trimmed edges are a close approximation rather than the exact curve. - Base material colors. Everything that depends on another file or on running behaviour is left out: `Inline` scenes are never fetched, prototypes (`PROTO`/`EXTERNPROTO`) are not expanded, and scripts, routes, sensors, animation, lines, points and textures are ignored. When something is left out, the result is marked incomplete and the warning names the reason. An X3D file that only references other files through `Inline` therefore opens with nothing to show; upload the referenced scene itself, or ask the sender for a STEP file. ## Check the units before you measure X3D measures length in metres by default, and since X3D 3.3 a file can declare another length unit with a `UNIT` statement. CADProps follows that rule: a file with an explicit length `UNIT` statement has a verified scale, and a file without one is read in metres and shown in millimetres. The second case is still an assumption, because some exporters write millimetre coordinates without declaring them. The scene is then marked as using assumed units, and area, volume and calculated mass stay unavailable. Before you quote a size from an X3D export, measure one feature whose real size you know. If a 50 mm hole reads 50,000 mm, the exporter wrote millimetres without a `UNIT` statement; the [scale factor guide](https://www.cadprops.com/guides/cad-model-wrong-scale-25-4/index.md) shows how to recognise this and other common factors. ## What an X3D export cannot tell you X3D stores what a viewer needs to draw the model, not how the model was built. There is no feature tree, no sketch constraints and no exact B-Rep surface to measure a true radius from. Even a NURBS patch in X3D is a display surface: CADProps turns it into triangles, and [tessellation](https://www.cadprops.com/guides/cad-tessellation/index.md) explains why a finer mesh still does not give back exact geometry. Volume and mass need a closed mesh with consistent orientation, which scene exports often lack; see [watertight meshes](https://www.cadprops.com/guides/watertight-cad-mesh/index.md). For manufacturing questions such as wall thickness, hole tolerance or exact volume, ask for the original CAD file or a STEP export. Use X3D to review shape, placement and part structure, or to convert the scene to a mesh format another program accepts. The [mesh format notes](https://www.cadprops.com/mesh-formats/index.md) compare X3D with STL, OBJ, 3MF, glTF, VRML and AMF, and the [format matrix](https://www.cadprops.com/supported-formats/index.md) lists every input and its limits. ## Sources - [Web3D Consortium X3D specifications](https://www.web3d.org/standards) ## Related reading - [CAD Tessellation: When a Solid Becomes a Triangle Mesh](https://www.cadprops.com/guides/cad-tessellation/index.md) - [GLB vs glTF for CAD: 3D Model Files, Assets and Units](https://www.cadprops.com/guides/glb-vs-gltf-for-cad/index.md) - [IGES File (.igs, .iges): What It Is and How to Open It](https://www.cadprops.com/guides/iges-file-what-it-is-how-to-open/index.md) - [OBJ Mesh Units and Volume: Check Scale and a Closed Shell](https://www.cadprops.com/guides/obj-mesh-units-and-closure/index.md) - [Open a Rhino 3DM File Without Rhino](https://www.cadprops.com/guides/open-3dm-without-rhino/index.md) - [Open CAD Files on Mac: STEP Viewers and Format Options](https://www.cadprops.com/guides/open-cad-files-on-mac/index.md) - [IFC Files: How to Open a BIM Model Online and What You Will See](https://www.cadprops.com/guides/open-ifc-file-online/index.md) - [UNV Files: What They Are and How to Open Them Online](https://www.cadprops.com/guides/open-unv-file-online/index.md) - [VDA-FS Files: What They Are and How to Open Them Online](https://www.cadprops.com/guides/open-vda-file-online/index.md) - [Watertight Mesh: When an STL Can Have a Volume](https://www.cadprops.com/guides/watertight-cad-mesh/index.md) Original article: https://www.cadprops.com/guides/open-x3d-file-online/ HTML page: https://www.cadprops.com/guides/open-x3d-file-online/