BREP is the native geometry format of the open-source CAD kernel that this site and many engineering tools are built on. It stores exact topology and geometry — faces, edges, vertices and the surfaces that carry them — with full fidelity for applications built on that kernel.
BREP is the native shape serialisation of the open-source CAD kernel, so it comes from tooling built on that kernel: shape exports from open-source CAD applications, CadQuery and build123d scripts, KiCad’s 3D pipeline, and command-line utilities dumping an intermediate result.
Best for: Moving exact geometry between tools built on the same CAD kernel. There is a fuller write-up on the BREP format reference page.
Every format on this site also gets the same viewport tools: orbit, pan and zoom with fit-to-view, isometric and the six standard views, a perspective/orthographic toggle, shaded, shaded-with-edges, wireframe and X-ray display, hide-selected, and a PNG screenshot of the current view. The same controls are on the general 3D and CAD viewer, which accepts every importable format at once.
Worth knowing before you rely on it. A viewer that overstates what it can read wastes more of your time than one that is specific about its limits.
| BREP files | |
|---|---|
| Extensions | .brep, .brp |
| Geometry | Exact B-rep topology |
| Units | Model units |
| Colors & materials | No |
| Animations | No |
| Typical use | Open-source CAD kernel workflows |
A BREP file does not declare units, so the numbers are the shape’s own coordinates with a millimetre label — right for the kernel’s usual convention, wrong if the script that wrote it worked in inches.
BREP is a source format here. To use the shape in a slicer, renderer or game engine, tessellate it into a mesh format. The converter runs on the same local pipeline as this viewer, so a conversion is just as private as a preview: BREP to STL is the usual choice.
CAD applications built on the same geometry kernel open it natively, and this page opens it in a browser tab using that kernel compiled to WebAssembly. There is no need to install a CAD application just to look at a shape.
Because a BREP file normally serialises a single shape rather than an assembly. If a compound was written, its solids appear as separate entries; otherwise you get one, and the exploded view stays disabled since there is nothing to separate.
They were never in the .brep file. BREP stores topology and geometry only. Export STEP from the CAD application instead if you need per-part colors and names to travel with the model.
No. The WebAssembly build of the CAD kernel runs in your tab and reads the bytes directly from the file you picked. Nothing is transmitted.
Geometry: exact b-rep topology. Units: model units. Colors and materials: no. Animations: no. Of that, the viewer draws geometry and flat base colors; texture maps and animation are never displayed. A BREP file does not declare units, so the numbers are the shape’s own coordinates with a millimetre label — right for the kernel’s usual convention, wrong if the script that wrote it worked in inches.
Read the BREP format reference for the format itself, open the general 3D and CAD viewer if you have several formats to look at, or start from the 3D and CAD converter.
The mesh simplifier does not read .brep directly. To bring a triangle count down, convert to STL first, then simplify that. If the file is headed for a 3D printer, the G-code viewer shows the sliced toolpath layer by layer once your slicer has run.