Convert STL to OBJ - Free Online Converter
Drop a .stl file below and download it as .obj in seconds. The conversion runs entirely in your browser - no upload, no signup, no watermark. Both binary and ASCII STL parse, and the output opens in every 3D tool.
Updated July 2026
Done in seconds
Your STL converts to OBJ locally in your browser - no upload queue, no waiting.
Private by design
Your file never leaves your device. Nothing is uploaded, nothing is stored.
Free, no strings
No signup, no watermark, no file limit - convert as many files as you need.
How to convert stl to obj
Drop your STL file
Drag the .stl file into the converter above or click to browse. No account and no upload - the file stays on your device.
Conversion runs in your browser
The model is parsed and rewritten locally, in seconds for typical files. Geometry is carried over 1:1 - no remeshing, no quality loss.
Download the OBJ
The .obj download starts from the same spot. Convert as many files as you like - there is no limit or watermark.
STL and OBJ, explained
What is STL?
STL is the oldest and most universal 3D printing format. It describes a model as a plain list of triangles - nothing else. No colors, no materials, no units, no object names. That simplicity is exactly why every slicer, CAD tool, and print service on earth accepts it.
An STL file stores each triangle as three corner points plus a facet normal, either as compact binary (the common case) or human-readable ASCII. Because the format carries no unit information, almost every tool assumes millimeters. When a file needs to work absolutely anywhere, STL is still the safe answer.
- Developed by
- 3D Systems (1987)
- Structure
- Binary or ASCII list of raw triangles
- Used by
- Every slicer, CAD package, mesh-repair tool, and 3D-printing marketplace
What is OBJ?
OBJ is the plain-text workhorse of 3D interchange. It stores vertices, faces, UV coordinates, and normals in a human-readable file, with materials referenced from a companion .mtl file. Practically every 3D application of the last 30 years can read it.
Because OBJ splits materials and textures into separate files, a bare .obj carries geometry and UVs but shows up untextured unless the .mtl and texture images travel with it. It has no units, no rigging, and no animation - which keeps it simple and universally compatible.
- Developed by
- Wavefront Technologies (circa 1990)
- Structure
- Plain-text geometry, with materials in a separate .mtl file
- Used by
- Blender, Maya, 3ds Max, ZBrush, game engines, 3D scanners
What survives the stl to obj conversion
Format conversion is honest work: some data has nowhere to go in the target format. Here is exactly what carries over.
Triangle geometry
Every triangle is carried over exactly - no remeshing or decimation.
Model scale
Both formats are unitless; coordinates copy 1:1, so print-scale millimeter numbers arrive unchanged.
Smooth shading normals
STL stores flat facets; vertex normals are computed during conversion so the OBJ shades smoothly where the geometry allows.
UV coordinates
STL has no UVs, so the OBJ has none either - the mesh must be UV-unwrapped before texturing.
Colors & materials
Standard STL stores no color, so there is nothing to carry - the OBJ is untextured geometry.
When should you convert STL to OBJ?
Convert to OBJ to take print files back into modeling tools: editing a downloaded STL, using it as a sculpting base, kitbashing, or importing into software whose OBJ support is better than its STL support.
If the file is only ever going to a slicer, leave it as STL - the conversion adds nothing for printing. Convert when the mesh's next stop is a 3D editor, engine, or renderer.
Still weighing the formats themselves? See the full STL vs OBJ comparison - structure, materials, file size, and which wins for each use case.
And if what you actually need is a new model rather than a new file format: 3D AI Studio's main tool can generate 3D models from photos with AI - with exports to every format on this page.
STL to OBJ - frequently asked questions
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