STL to OBJ Converter
Convert between STL and OBJ 3D file formats instantly in your browser. Drop your file, preview the model in 3D, and download the converted file. Completely free and private — your files never leave your device.
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How STL to OBJ Conversion Works
Three-dimensional file formats serve different purposes in the 3D workflow. STL (Stereolithography) and OBJ (Wavefront) are two of the most common formats, each with distinct strengths. This tool lets you convert between them directly in your browser, with no uploads, no sign-ups, and no file size limits beyond your device's memory.
Understanding STL Format
STL is the standard file format for 3D printing. Developed by 3D Systems in 1987, it describes only the surface geometry of a three-dimensional object using a collection of triangular facets. Each triangle is defined by three vertices and a face normal vector. STL files come in two varieties: ASCII (human-readable) and binary (compact). Binary STL is far more common because it produces smaller files. Because STL only stores raw triangle data, it cannot represent colors, textures, materials, or any metadata beyond geometry.
Understanding OBJ Format
OBJ is a widely supported 3D model format created by Wavefront Technologies. Unlike STL, OBJ can store vertex positions, texture coordinates (UVs), vertex normals, and material references through companion MTL files. This makes OBJ the preferred choice for 3D modeling, rendering, and game development workflows. Most 3D software — including Blender, Maya, 3ds Max, Cinema 4D, and Unity — can import and export OBJ files natively.
When to Convert STL to OBJ
If you have a 3D-printable STL model and want to edit it in a modeling application, converting to OBJ makes it easier to import. OBJ is more universally supported in creative software and allows you to assign materials, adjust normals, and add texture coordinates after conversion. This is common when repurposing 3D print models for visualization, animation, or game assets.
When to Convert OBJ to STL
If you have a 3D model in OBJ format and need to send it to a 3D printer or a slicing application like Cura, PrusaSlicer, or Bambu Studio, you need STL. Slicers expect triangle mesh data without materials or textures. Converting OBJ to STL strips away material data and produces a clean triangle mesh ready for printing.
Format Comparison
STL: Triangles only → ideal for 3D printing, slicing, FEA simulation
OBJ: Vertices + normals + UVs + materials → ideal for modeling, rendering, game dev
Quality: Geometry is preserved exactly. STL→OBJ adds no data; OBJ→STL discards materials and UVs.
Privacy and Performance
This converter uses Three.js to parse and export 3D files entirely in your browser. Your models are never uploaded to any server. The conversion runs on your device's CPU, so even large files with hundreds of thousands of triangles convert in seconds. There are no file size restrictions — you are limited only by your browser's available memory. This makes it suitable for sensitive design files, proprietary models, or simply avoiding slow upload-and-download cycles.
Frequently Asked Questions
What is STL format?
STL (Stereolithography) is a file format that describes only the surface geometry of a 3D object using triangular facets. It is the most common format for 3D printing because slicing software expects triangle meshes without materials or textures.
What is OBJ format?
OBJ (Wavefront) is a widely supported 3D model format that stores vertex positions, normals, texture coordinates, and material references. It is commonly used in 3D modeling, animation, and game development because it supports richer data than STL.
Is my file uploaded anywhere?
No. This converter runs entirely in your browser using JavaScript and Three.js. Your 3D files are never uploaded to any server. Everything stays on your device.
Does conversion lose quality?
The geometry is preserved exactly during conversion. However, STL only stores triangle mesh data, so converting OBJ to STL will discard texture coordinates, materials, and vertex normals beyond face normals. Converting STL to OBJ preserves all geometry data.
Can I convert GLTF files?
This tool currently supports STL and OBJ formats. GLTF/GLB conversion requires additional handling for materials, animations, and embedded textures. We may add GLTF support in a future update.
Why convert STL to OBJ?
You might convert STL to OBJ when importing a 3D-print-ready model into a 3D modeling application like Blender, Maya, or 3ds Max. OBJ is more widely supported in modeling software and allows you to add materials and textures.