3D Convert How to convert STL to OBJ
Going from STL to OBJ is easy; the interesting part is what an STL never had in the first place.
Steps
- Open the mesh converter.
- Drop your
.stlfile on the page. It is read on your machine; nothing is sent anywhere. - Pick OBJ in the format list.
- Press Convert. In Chrome or Edge you choose the destination file first and the result is written to it as it is produced, so the size of the output is limited only by your disk.
Both binary and ASCII STL are accepted, and detected from the contents rather than the extension — including the binary files whose header begins with the word solid, which trips up readers that sniff for that word alone.
The vertex count will look wrong
An STL stores three full positions per triangle with no index, so a cube with 8 corners is stored as 12 triangles × 3 corners = 36 vertices. Convert it and the OBJ has 36 vertices, not 8. The shape is identical; the duplicates are simply what the STL contained.
Merging those duplicates back into shared vertices is called welding. It is not a lossless operation — deciding which nearby positions are "the same" requires a tolerance, and picking it wrong either leaves cracks or fuses parts that should stay separate. This converter does not guess: it gives you exactly the geometry the STL held. Blender, MeshLab and most CAD tools offer a merge-by-distance step where you choose the tolerance yourself.
What you will not get
No colour, no texture coordinates, no material. An STL never had them. If your source is really a coloured scan that was flattened to STL earlier in the pipeline, that colour is gone for good — go back to the file before the STL if you can, and use PLY next time.