STL to OBJ Converter — Edit 3D Print Files, No Upload

Yes, and this is the main reason people do this conversion. When you import the OBJ into Blender (File > Import > Wavefront), the mesh has proper vertex indexing — meaning shared vertices between faces are actually shared, not duplicated like in STL. This unlocks every Edit Mode tool: loop cuts work correctly, bevel follows edge flow, subdivision surface produces smooth results instead of weird artifacts. Boolean operations work reliably because the mesh topology is clean. One gotcha: if the original STL had disconnected shells (common in multi-part print models), the OBJ will have them too. Use Blender's Select Linked (L key) to isolate individual shells before editing.

No — the converter can't create information that doesn't exist. STL is geometry-only, so the OBJ will also have no .mtl file. In Blender, the imported mesh will be the default gray. To add materials: select the mesh, go to the Material Properties panel, click "New", and assign colors/textures. If you're planning to render the model (for a product photo or portfolio shot), start with a Principled BSDF shader — it gives realistic results with minimal setup. Set Base Color to your desired color, Roughness to 0.4-0.6 for plastic, Metallic to 1.0 for metal parts.

Vertex positions are preserved exactly — no rounding, no scaling. But here's where people get confused: STL files from 3D printing workflows are almost always in millimeters, while Blender's default unit is meters. So a 50mm figurine shows up as 50 meters tall in Blender. The fix depends on your workflow: (1) In Blender: set Scene Properties > Unit Scale to 0.001 before importing, or select the imported object and scale by 0.001. (2) In Maya: the import dialog has a Scale field — set it to 0.1 if importing mm-scale STL. (3) Don't resize the OBJ file itself — keep the original coordinates and adjust your software's interpretation.

Two separate questions here. Legally: most Thingiverse models use Creative Commons licenses — check the model page for the specific license. CC BY means you can remix with attribution. CC BY-NC means non-commercial only. CC BY-SA means your remix must use the same license. Some models are "All Rights Reserved" which technically means no remixing. Practically: nobody enforces this for personal use, but if you're selling the remix, respect the license. Technically: yes, this is exactly what STL-to-OBJ conversion is for. Convert here, import to Blender, modify (extrude, boolean, sculpt), then export back to STL when you're done. The round-trip is lossless for geometry.

It comes down to how each format stores vertices. STL uses "triangle soup" — every triangle stores all three vertex coordinates independently, even when adjacent triangles share a vertex. A cube has 12 triangles × 3 vertices = 36 stored vertices, even though a cube only has 8 unique vertices. OBJ uses indexed vertices: each unique vertex position is stored once, and faces reference them by index number. That same cube uses 8 vertex entries + 12 face entries. In practice, a typical mesh shares each vertex between 4-6 faces, so OBJ is roughly 40-60% smaller than ASCII STL. Compared to Binary STL, OBJ is about the same size — Binary STL already compresses the coordinate data.

This usually means the STL had inconsistent face normals — some faces pointing inward, some outward. The converter preserves normals as-is. Fix in Blender: select the mesh, go to Edit Mode, select all (A), then Mesh > Normals > Recalculate Outside (Shift+N). If that doesn't fully fix it, look for non-manifold edges: Select > All by Trait > Non Manifold. These are usually duplicate vertices or zero-area faces from the original STL. Clean them up with Mesh > Clean Up > Merge by Distance (threshold 0.0001).