STL → OBJ · FREE · NO UPLOAD
STL to OBJ Converter — For Editors That Want OBJ
Turn a .stl into a clean .obj for Blender, Maya, CAD importers and asset stores — in the browser, nothing uploaded.
What it does: converts an STL to Wavefront OBJ by indexing shared vertices and writing v/vn/f text lines. The output is a clean, editor-friendly mesh — no repeated vertices, no binary blob.
Why you need it:OBJ is the lingua franca of 3D editors (Blender, Maya, ZBrush) and asset marketplaces. STL's repeated-vertex binary format is hard to edit; OBJ gives you indexed faces and human-readable text.
How it works: three.js indexes the mesh and writes OBJ text in this browser tab. No server, no upload — disconnect and it still runs.
Conversion specs
| Input format | STL (binary or ASCII) |
| Output format | Wavefront OBJ (text-based, indexed v/f format) |
| Vertex indexing | Shared vertices welded — cleaner topology for editing |
| Unit mapping | Numbers copied as-is (neither format specifies a unit) |
| MTL file | Not generated (STL carries no color or material) |
| File size limit | Device RAM only — no server limit |
| Processing | 100% client-side via three.js OBJExporter |
| Cost | Free, unlimited conversions, no account required |
Into Blender for editing, back out for printing
Sometimes the STL is close but not done: you need to cut a hole, thicken a wall, or boolean a logo before it goes back to the slicer. Blender is a common place to do that work, and Blender is happier with OBJ than with a raw STL triangle soup. This page is the inbound conversion. The outbound conversion is Blender's own STL export.
- Drop the STL on the converter above. Download the OBJ. Open that OBJ in Blender and edit it. When the mesh is right, export a print file with File → Export → STL. Open that STL in Bambu Studio or PrusaSlicer and slice as usual. Nothing in this hop changes the triangles on the way in; vertex positions are written in plain text. You will not get a .mtl — an STL has no material to carry over — and Blender will open a material-less OBJ without complaint.
- The unit trap is the step people skip. Blender's default scene unit is meters. Slicers assume STL numbers are millimeters. A 40 mm bracket stored as 40 in the STL arrives in Blender as a 40-meter object if you take the numbers literally, or as a speck if a later export writes meters back out as millimeters. Before you trust the first slice, check dimensions in the viewer. The homepage preview shows bounding-box size in the model's native units. If a part that should be 40 mm reads as 0.04 or 40,000, you know whether to scale in Blender or in the slicer before you print.
- A practical order that avoids that surprise: convert STL to OBJ here, glance at the bounds so you know the number you are about to import, edit in Blender at whatever scale is comfortable, then File → Export → STL and look at the new file in the viewer again. Only then open the slicer. If you needed a web preview rather than an editable mesh, use STL to GLB instead. If you are going the other way — an OBJ sculpt toward the printer — that is OBJ to STL.
That loop is the whole point of this page: STL in, OBJ out, Blender in the middle, STL back to the printer. Keep the meter-versus-millimeter check in the viewer and the round-trip stays boring, which is what you want from a format conversion.
FAQ
Is the STL uploaded to convert it?+
No. Parsing and OBJ writing both happen in this tab with JavaScript. There is no upload endpoint; the tool works offline once the page has loaded.
Why OBJ instead of STL?+
Some tools and marketplaces simply prefer OBJ: older 3D packages, certain CAD importers, texture-painting workflows, asset stores. OBJ also stores the mesh as indexed vertices, which many editors handle more gracefully than STL's repeated-vertex triangle soup.
Does the OBJ include materials?+
No .mtl is generated — an STL has no color or material to carry over. Editors open material-less OBJ files without complaint and let you assign materials there.
Is geometry changed in any way?+
No. Every triangle crosses over exactly; vertex positions are written in plain text with full precision. The OBJ will be larger than the binary STL because text encoding is verbose — that's expected.
Related: OBJ to STL (the reverse), STL to GLB for web and AR use.