Why does the tool reject my mesh?

The Boolean kernel requires a watertight, consistently oriented manifold. Use clean-mesh, fill-holes, unify-normals or repair-non-manifold first, then try again.

Why is the result empty?

Subtract and intersect need overlapping solids. If B does not intersect A, subtract returns A and intersect may be empty; the tool reports an empty result instead of downloading a blank STL.

Are the files uploaded?

No. Both files are parsed and combined inside a Worker on this device; the Manifold WASM module is served as a static file.

Can I use a GLB or glTF file?

Yes, if it contains triangle geometry and is closed and manifold. External buffers are not supported; use a self-contained glTF or GLB.

Why does boolean fail with a manifold error?

Both inputs must be closed, watertight, and consistently oriented. Run repair-non-manifold or repair-all on each part first; open or self-intersecting shells are rejected before the boolean.

Transform & optimize/Optimize

Boolean mesh operations (local)

Combine two closed meshes with a union, difference or intersection locally. The Worker parses both files, cleans and validates their topology, runs the boolean with Manifold WASM, and downloads the result as binary STL without uploading either model.

ReadyNo uploadWorkerSTL · OBJ · PLY · 3MF · GLB · glTF

Tool facts

Formats: STL · OBJ · PLY · 3MF · GLB · glTF
Output: Mesh file
Worker: Yes
Max file: 500 MB
Runs: in your browser

Why local

Boolean result

No upload

Boolean result

Both inputs must be closed, consistently oriented manifolds. The boolean runs locally in the Worker with Manifold WASM; the result is checked for manifold topology before download.

Boolean result

STL, OBJ, PLY, 3MF, GLB, or a self-contained glTF. Both meshes must be closed, consistently oriented manifolds.

Boolean operation · Union (A ∪ B)

Mesh A

STL, OBJ, PLY, 3MF, GLB, or a self-contained glTF. Both meshes must be closed, consistently oriented manifolds.

Choose a file

Max file size: 500 MB · No upload

Mesh B

STL, OBJ, PLY, 3MF, GLB, or a self-contained glTF. Both meshes must be closed, consistently oriented manifolds.

Choose a file

Max file size: 500 MB · No upload

Boolean operation

No upload · Manifold WASM runs in the Worker.

How it works

1
Drop Mesh A and Mesh B in STL, OBJ, PLY, 3MF, GLB or self-contained glTF format.
2
Choose union, subtract (A − B), or intersect.
3
The Worker welds and cleans both meshes, then verifies that each is closed, watertight and consistently oriented.
4
Manifold WASM computes the boolean in the Worker and the result is checked for manifold topology.
5
Download the result as binary STL.

What the numbers mean

Operation

Union merges the occupied volumes, Subtract removes B from A, and Intersect keeps only the shared volume. Subtraction is ordered: A − B is not B − A.

Inputs

Both inputs must be closed, consistently oriented manifolds. Open surfaces, flipped winding and non-manifold edges are rejected rather than silently repaired.

Output

The result is a single manifold mesh. Its triangle count can be much higher than either input because intersections add new edges and faces.

Limits

Manifold is a boolean engine, not a repair tool. Coplanar overlaps and very large meshes can still fail or be slow; run clean-mesh, fill-holes, unify-normals or repair-non-manifold before retrying.

Printing notes

Keep the two input files closed and consistently oriented; check each with manifold-check before boolean.
For a subtract operation, place the cutter so it fully crosses the target wall; a cutter that only touches a surface can create a zero-thickness result.
The output is a new mesh; keep the source files if you may need to revise the operation.
Inspect the result in a slicer, especially around newly created intersection edges.

Questions

References

· ISO/ASTM 52900
· Manifold: robust Boolean operations for triangle meshes