Will my model’s colors and textures carry over to the STL?

No, and this is expected behavior, not a limitation of this tool — STL has no concept of color, material, or texture at all. It only describes a triangle mesh surface, which is exactly what 3D printing slicers need and nothing more.

Why would I need to convert OBJ to STL specifically for 3D printing?

Nearly every desktop and online slicer (the software that turns a 3D model into printer instructions) expects STL or the similar 3MF format as input. OBJ is a general 3D interchange format most slicers don’t accept directly.

Is the output ASCII or binary STL?

Binary, which is the more compact and universally accepted variant — every modern slicer reads binary STL without issue, and it produces meaningfully smaller files than ASCII STL for complex models.

Will the converted model still be watertight / printable?

The conversion preserves your source geometry exactly as described in the OBJ — if the original mesh was watertight (manifold, with no holes), the STL will be too. This tool doesn't repair non-manifold geometry; that's a separate mesh-repair step some slicers handle automatically.

Can I convert an OBJ that references a separate .mtl material file?

Yes, the OBJ will load and convert even if its referenced .mtl file isn’t provided — material references are simply ignored during the STL export, since STL has no use for them.

Is there a polygon count limit?

No hard limit is built into the tool. Very high-poly models will take longer to parse and export and use more browser memory, but there's no server-imposed restriction.

Is my 3D model uploaded anywhere during conversion?

No. three.js parses and re-exports the geometry entirely in your browser — your model file never leaves your device.

Does this work with models that have multiple separate objects/groups?

Yes, an OBJ containing multiple named objects or groups converts them all into one combined STL mesh, since STL has no concept of separate named parts.

Will non-triangular faces (quads, n-gons) convert correctly?

Yes, three.js’s OBJLoader automatically triangulates quad and n-gon faces during parsing, so the resulting STL is always a proper triangle mesh regardless of your source OBJ’s face types.

Does this change or delete my original OBJ file?

No. The tool only reads the source file to generate a new, separate STL file — your original .obj file is left completely untouched.

OBJ to STL Converter — Free Online, No Upload

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What is OBJ to STL?

STL is the format nearly every 3D printer slicer expects — a deliberately minimal representation storing just a model's surface as a mesh of triangles, with no color, material, texture, or scene information at all. OBJ, by contrast, is a richer general-purpose 3D format that can carry materials and texture coordinates alongside geometry. This tool strips an OBJ model down to pure triangle geometry and re-packages it as STL, which is exactly what slicing software (Cura, PrusaSlicer, Bambu Studio, and similar) needs to generate print instructions.

The conversion runs through three.js, the standard JavaScript 3D library: OBJLoader parses your OBJ's vertex and face data into a scene graph, and STLExporter walks that geometry and writes out STL's triangle-list format. Because STL has no concept of materials or textures, anything beyond raw geometry in your source OBJ — colors, UV-mapped textures, named materials from an accompanying .mtl file — is intentionally dropped; only the shape survives, which is the correct and expected behavior for a format whose entire purpose is describing a solid for manufacturing.

Output is generated as binary STL by default, which is more compact than ASCII STL and is universally accepted by every modern slicer, though the underlying geometry is identical either way.

Need to go the other direction and get an editable OBJ back from an STL? Use STL to OBJ.

How It Works

Your OBJ file's text content is parsed by three.js's OBJLoader into a scene graph of mesh objects, reconstructing the vertex positions, faces, and normals the OBJ format describes. STLExporter then walks that geometry and serializes every triangle as STL's binary triangle format (12 bytes each for the normal and three vertices, plus a 2-byte attribute count), producing a complete, spec-compliant binary STL file.

How to Use

Upload your OBJ file

Drop a .obj file onto the upload area, or click to browse for it.

Click Convert to STL

three.js parses the geometry and re-exports it as binary STL.

Download the STL file

Save the result — it keeps your original filename with a .stl extension.

Open in your slicer

Import the STL directly into Cura, PrusaSlicer, Bambu Studio, or any other slicing software.

Who Uses This Tool

🖨️

3D Printing Prep

Convert a downloaded or modeled OBJ into the STL format every slicer expects.

🎨

3D Modeling Handoff

Prepare a model exported from Blender, SketchUp, or similar software for print.

🏗️

Rapid Prototyping

Convert design iterations into print-ready STL files quickly during development.

📐

CAD-to-Print Pipelines

Bridge OBJ exports from CAD or modeling tools into a 3D printing workflow.

🎮

Game Asset Prototyping

Turn a game asset modeled in OBJ into a physical prototype via 3D printing.

🧩

Miniatures & Figurines

Convert downloaded or custom-modeled miniature designs for tabletop printing.

Why Choose This Tool

Standard three.js Pipeline

Uses the same parsing and export logic powering countless production 3D web tools.

Slicer-Ready Output

Binary STL works directly in every major 3D printing slicer with no further conversion.

Fully Local Processing

Parsing and export both happen in your browser — nothing is uploaded.

Exact Geometry Preservation

Vertex positions and triangulation are preserved precisely from source to output.

No Server-Side Size Cap

Local processing means no artificial ceiling on model complexity beyond your account plan.

Free, No Watermark

Free with no account for files under 40MB; sign up free for 80MB or go Pro for 250MB.

Key Benefits

Uses three.js, the standard JavaScript 3D library

Output works directly in any slicer (Cura, PrusaSlicer, Bambu Studio)

Browser-based — your model is never uploaded to a server

Binary STL output — compact, universally supported

Preserves exact geometry, vertex positions, and triangulation

No file size limit beyond your browser's available memory

No account needed for standard file sizes

100% free with no watermark

Frequently Asked Questions

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OBJ to STL