Convert STL to OBJ
Free online STL-to-OBJ converter. No sign-up, no upload, no watermark — it runs entirely in your browser.
Drop your STL file here
or click to browse · we convert it to OBJ instantly
100% in your browser — your file never leaves your device.
STL is a dead end the moment you leave the print world: no UVs, no materials, no named parts, and it isn't even in the import dialog of half the tools I use. Unity and Unreal won't take it, Substance Painter won't, Mixamo won't. OBJ gets the mesh through the door. This converter also welds the STL's loose triangles into one connected mesh on the way — which is the difference between a model you can sculpt, smooth and decimate and a soup of 200,000 disconnected faces.
Converting STL (stereolithography) to Wavefront OBJ
STL is geometry-only and everywhere in 3D printing, but many 3D apps and pipelines prefer OBJ — just as portable and ready to receive materials and UVs. Converting STL to OBJ makes a printable mesh easy to import and texture.
What's kept and what's dropped
Geometry is preserved exactly. The output OBJ has no materials yet (STL carried none) — you can assign materials and UVs in your 3D app afterwards.
What this conversion is actually for
A scan that needs texturing
Desktop scanners hand over STL by default. Substance Painter's import list is OBJ, FBX, glTF, USD and Alembic — no STL — so it's STL → OBJ here, then a quick unwrap in Blender before the mesh will hold a texture at all.
A Thingiverse prop for a game scene
Unity has no STL importer and neither does Unreal. Convert to OBJ, drop it in — then face the real problem: a printable prop is usually 300k–2M triangles, so it wants retopology or a Decimate pass down to something a game can draw sixty times a second.
Auto-rigging a printable character
Mixamo accepts OBJ and FBX. A character STL converts here, uploads there, and comes back rigged — provided it's a single connected humanoid mesh in a T- or A-pose, which the welding step helps with and a slicer-oriented model made of floating parts will not be.
How to convert STL to OBJ
- 1Drop your STL file onto the box above, or click to browse for it.
- 2Sculptor converts it to OBJ right in your browser — nothing is uploaded.
- 3Your OBJ file downloads automatically. That's it.
Before you trust the OBJ: 4 checks
- No UVs yet
- STL never had texture coordinates, so the OBJ has none. Before texturing: Blender → Edit Mode → select all → U → Smart UV Project is the thirty-second version; the UV unwrapping guide covers doing it properly.
- Shading
- The OBJ is written without baked normals on purpose — your 3D app computes them on import, so a hard-edged CAD part stays crisp (Shade Flat) and a figure can be smoothed (Shade Auto Smooth) instead of inheriting one wrong guess for both.
- One object
- An STL is one solid, so the OBJ is one object. Separate shells — a base, a body, an accessory — come apart with Mesh → Separate → By Loose Parts (P) in Blender.
- Triangle count
- Print meshes are dense. If the STL viewer showed a million triangles, plan a Decimate modifier (ratio 0.1–0.3) or a proper retopology before this goes anywhere real-time.
New to these formats? Read what an STL file is and what an OBJ file is. Check the result in the free OBJ viewer before it goes anywhere.
STL to OBJ — FAQ
- Why does an STL open as a 'triangle soup' in Blender, and does this fix it?
- STL stores every triangle on its own — three private vertices each, nothing shared — so a naive conversion gives you a mesh where no face is connected to its neighbour: no edge loops, no smooth shading, and sculpting tears it apart. This converter welds coincident vertices as it converts, so the OBJ opens as one connected mesh with roughly a third of the vertex count. It's the same as running Merge by Distance in Blender, done for you.
- Does the OBJ come with a .mtl material file?
- No, and it can't: an STL has no colour or material to describe, so there's nothing to write. Your 3D app will show the mesh in its default grey. Assign materials after unwrapping — a material without UVs has nowhere to go.
- Will it be the right size?
- The numbers don't change. Slicers treated them as millimetres; Blender and Unity treat OBJ units as metres by default, so a 120 mm print reads as 120 metres until you set the import scale (Blender's OBJ importer has a Scale field — type 0.001).
- Can Blender just import STL directly?
- Yes, and if you're in Blender that's the shortest path. This page is for the tools that can't — Unity, Unreal, Substance Painter, Mixamo, most web pipelines — and for the machine that doesn't have Blender on it.
- Is anything uploaded?
- No — the STL is parsed, welded and rewritten inside your browser tab; nothing is sent to a server. Confidential scan data stays on your machine.
- Will it round-trip back to STL for printing later?
- Yes: OBJ holds triangles just as faithfully, and OBJ to STL on this site takes it straight back. What won't survive the round trip is anything you add in between — UVs and materials are stripped again on the way back to STL.
Need a model you don't have yet?
Describe it or upload an image — Sculptor generates a fresh 3D model across the best AI engines, then exports it in OBJ and more.
Generate a 3D modelPrinting something? See the AI-for-3D-printing guide