Upload an STL file and download a glTF model for the web.
Input file
Everything runs in your browser — your files are never uploaded. STEP/IGES use the OpenCASCADE engine (a one-time ~7 MB download) and are tessellated into a mesh, so the result is a surface model, not editable CAD history.
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What is the STL to glTF?
An STL to glTF converter is an online tool that transforms Stereolithography (.stl) files into GL Transmission Format (.gltf or .glb) files. STL is a triangulated surface format widely used in 3D printing and CAD workflows; glTF is a standardised, compressed transmission format designed for web, mobile, AR, and real-time 3D applications. The converter preserves the geometric mesh, applies unit scaling, and packages the model for efficient streaming.
How it works
The converter reads the binary or ASCII STL file, extracts the mesh geometry (vertices and triangle faces), performs optional scale normalisation to match glTF conventions (often millimetres to metres), and re-encodes the model as glTF/glb with embedded geometry. The output glTF file can include materials, normals, and metadata; glb is a single-file binary package ideal for web delivery. Most converters embed textures or offer separate material configuration.
bracket.glb (320 KB, with computed vertex normals for smooth shading)
Vertex normals are calculated to improve visual quality in web viewers; no material information added; suitable for inspection or sharing
How to use the STL to glTF
Upload your STL file (binary or ASCII format, any size up to limit)
Choose output format: glTF separate (.gltf + .bin) or glb single-file binary
Set unit scale (e.g. mm to m) if your CAD used different units
Click Convert and download the glTF or glb file instantly
Test in a web viewer (three.js, Babylon.js, Sketchfab) or integrate into your app
Re-export from web viewers or game engines if you need further refinement
Benefits
Instant conversion—no CAD software needed, works in the browser
glTF is a W3C standard supported by all major 3D frameworks and AR platforms (Apple ARKit, Google ARCore, WebAR)
Dramatically smaller file sizes (often 70–90% compression vs STL binary) for faster streaming to mobile and web
glb single-file format eliminates texture and material path headaches
Preserves precise geometry and scale for engineering, product review, and medical 3D workflows
Compatible with Blender, Unreal Engine, Unity, Three.js, Cesium.js, and most modern 3D tools
Tips & common mistakes
Common mistakes
Forgetting to set the correct input unit (mm, cm, m)—glTF assumes metres, so a model scaled by 1000× will appear tiny or huge in viewers
Uploading STL files with very high polygon counts (>1 million triangles) without decimation; resulting glb can still be too large for mobile or AR
Assuming textures and materials convert automatically; STL is geometry-only, so you must add materials in the target app (Three.js, Babylon.js, etc.)
Not validating the output in a viewer before using in production; mesh corruption or inverted normals (back-lit faces) are rare but detectable only visually
Tips
For AR/VR: glb is preferred over split glTF because it's a single download; keeps network payloads minimal on mobile
Decimate high-poly STLs (>500k triangles) in Blender or Meshlab before conversion to keep web delivery fast and smooth on lower-end devices
Use glTF if you plan to add materials, animations, or metadata later—the separate .bin and texture format is more modular in production pipelines
Check normals after conversion: if your model looks dark or inside-out in a viewer, you may need to flip face winding or recalculate normals in Blender
Frequently asked questions
Can I convert STL to glTF offline or in bulk?
Yes. Command-line tools like Assimp, OpenCTM, and gltf-pipeline can batch-convert hundreds of files locally. For web-based bulk conversion, some converters offer batch upload; check the FreeTooz upload limits.
Will my model's colour or texture convert from STL to glTF?
No. STL is a geometry-only format with no built-in colour or texture data. You must apply materials and colours in your 3D viewer (Three.js, Babylon.js) or re-assign textures after conversion in tools like Blender.
What is the difference between glTF and glb?
glTF is a JSON manifest + separate binary files (.bin, images, etc.); glb is a single compressed binary package. glb is faster for web because it's one download; glTF is better for editing and modular pipelines.
Can I preserve scale and units when converting STL to glTF?
Yes. Specify your input units (mm, cm, inches) and the converter will scale to glTF metres. Always verify scale in a web viewer after conversion to confirm the model is life-sized.
Is glb smaller than the original STL?
Almost always. glb uses binary compression and optimised mesh representation. Expect 70–90% smaller files than binary STL, and even more vs ASCII STL. A 10 MB STL often becomes 0.5–2 MB glb.
Can I import a converted glTF file into Blender, Unity, or Unreal?
Yes. All three support glTF and glb natively. Open or drag-and-drop the converted file into the editor. Scale, materials, and animations can be applied in the host application.