Convert OBJ to STL - Free Online Converter
Drop a .obj file below and download it as .stl in seconds. The conversion runs entirely in your browser - no upload, no signup, no watermark. Every face of your mesh is carried over 1:1 into a binary STL that any slicer or print service accepts.
Updated July 2026
Done in seconds
Your OBJ converts to STL 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 obj to stl
Drop your OBJ file
Drag the .obj 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 STL
The .stl download starts from the same spot. Convert as many files as you like - there is no limit or watermark.
OBJ and STL, explained
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 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 survives the obj to stl conversion
Format conversion is honest work: some data has nowhere to go in the target format. Here is exactly what carries over.
Mesh geometry
All faces are carried over exactly; polygons are triangulated the same way every 3D tool does it. No decimation or smoothing.
Model scale
OBJ and STL are both unitless - the numeric coordinates are copied 1:1. If the model was designed in millimeters it slices at the right size.
Multiple groups/objects
OBJ groups are merged into a single STL mesh (as separate shells) - STL has no object separation.
Materials (.mtl) & textures
STL stores bare triangles only. Materials live in the separate .mtl file anyway, which no STL can reference.
UV coordinates & normals
STL has no UV concept; face normals are recomputed from the triangles themselves, which is what slicers use.
When should you convert OBJ to STL?
Convert to STL when the model is headed for a 3D printer: slicers, print services, and mesh-repair tools are built around STL. It is also the standard upload format on most model marketplaces.
Keep the OBJ when appearance matters: it carries UV coordinates and references materials and textures that STL physically cannot store. For rendering, game engines, or texturing work, OBJ (or better, GLB) is the right side of this conversion.
Only have a picture, not a 3D file? The image to STL converter turns photos and logos into printable models.
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.
OBJ to STL - frequently asked questions
Made with 3D AI Studio
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