twineconvert

free · in-browser · no upload

STL to GLB
Converter

Drop your STL file. We'll convert it to GLB right here in your browser, your file never leaves your device.

or drop your file

Select your file here to get started

or drop your file here.

Accepts .stl

nothing uploaded no file size cap no signup

How it works

Three steps. No upload, no signup.

  1. 1

    Drop your file

    Click the dropzone above or drag a STL from your desktop. Files of any size, there's no upload, so there's no upload limit.

  2. 2

    Convert in your browser

    The conversion runs entirely in this tab using JavaScript and WebAssembly. Your file never touches our servers, we don't have any.

  3. 3

    Download

    Get your GLB the moment the conversion finishes. Convert another, or close the tab.

Files stay on your device

Your file is never uploaded. The entire conversion runs in your browser using WebAssembly. We can't see what you convert because we have no server to see it.

No file size limit

Server converters cap free users at 1-2 GB and gate larger files behind a paid plan. Since nothing uploads, our limit is whatever your browser can handle.

Free, no signup, no ads on conversions

No account required. No watermark on the output. No queue. Drop a file, get a converted file.

Why convert STL → GLB

What this conversion is actually for

STL is the 3D-printing standard but it's bad for web embedding: no scene graph, no compression, no streaming. GLB (glTF 2.0 binary) is the web-native format that powers Three.js, model-viewer, Sketchfab, Facebook 3D, Apple QuickLook (via USDZ), and every WebXR/AR pipeline. Converting STL to GLB unlocks browser-based 3D viewing, AR product previews, and embeddable 3D widgets on any webpage.

A real example

You designed a part in Fusion 360 and exported `part.stl` for the 3D printer. Now you want to embed an interactive 3D preview on your product page. Convert to `part.glb`, drop it next to your HTML, and reference it with `<model-viewer src="part.glb" auto-rotate camera-controls>`. Users can spin the model in any browser, including mobile AR.

Troubleshooting

The model loads but appears black / has no surface color in model-viewer.

Our STL→GLB converter only emits geometry (vertex positions + indices), not material data, because STL has no material concept either. Add `--exposure 1 --shadow-intensity 1` attributes to model-viewer, or add a material via Blender (File → Import .glb → Material tab → Add → File → Export .glb). Adding lighting in model-viewer (`<model-viewer environment-image="neutral">`) usually fixes it.

The browser says the GLB is too large to load.

STL meshes from CAD exports often have far more triangles than necessary for web display. Open in Blender → Modifiers → Decimate → set ratio to 0.1-0.3 to cut triangle count 70-90% before exporting to STL → re-run this converter. The visual difference at typical model-viewer sizes is imperceptible.

Formats involved

About STL and GLB

STL, Stereolithography

STL is the lingua franca of 3D printing, every slicer (PrusaSlicer, Bambu Studio, Cura, Simplify3D) reads it. Files are unstructured triangle soup: no scene graph, no materials, no scale info, just vertices and triangles. The format is ancient (1987) and primitive but its simplicity is exactly why it's universal. Two variants: ASCII (human-readable, big) and binary (compact, what most software produces).

How to open

Every 3D printing slicer, every CAD/3D tool (Blender, FreeCAD, Fusion 360, SolidWorks, Tinkercad). Free viewers: ViewSTL, MeshLab, online STL viewers.

Full STL format guide →
GLB, glTF 2.0 Binary

GLB is the binary container for glTF 2.0 — the Khronos Group's web-native 3D format, often called "the JPEG of 3D." A single .glb file packs the model's JSON metadata (scene graph, materials, animations) and binary buffers (vertex positions, normals, UVs, indices, textures) into one self-contained download, ideal for streaming over HTTP. Universal support across the modern 3D stack: Three.js, Babylon.js, model-viewer (Google's `<model-viewer>` web component), Sketchfab, Facebook 3D posts, Microsoft 3D Viewer, Apple QuickLook (via USDZ conversion), Blender (import/export), Unreal Engine, Unity. Every WebXR/AR/VR pipeline reads GLB. Spec finalized in 2017 as glTF 2.0; binary chunk format kept stable since.

How to open

Drag-and-drop into https://gltf-viewer.donmccurdy.com or https://sandbox.babylonjs.com/. Blender opens .glb via File → Import → glTF 2.0. The `<model-viewer>` web component renders them on any webpage with `<model-viewer src="model.glb">`. Microsoft 3D Viewer (Windows) and macOS Preview (with USDZ Tools) handle GLB natively.

Full GLB format guide →

Related tools

Convert other files to GLB

Convert your STL to other formats

FAQ

Common questions

Is this STL → GLB converter really free?

Yes. No signup, no watermark, no daily file count limit. Every conversion runs in your browser, your file never touches our servers because there are no servers.

Where does my file go when I convert it?

Nowhere. The conversion runs entirely in your browser using JavaScript and WebAssembly. Your file is never uploaded to our servers. We don't have any servers handling files, there's nothing for us to log, store, or accidentally leak.

What's the maximum file size?

Whatever your browser can hold in memory. Practically, this means a few hundred MB on most computers, significantly larger than the 1-2 GB caps that server-upload converters charge for. Very large files (multi-GB) may require closing other browser tabs first.

Why convert STL to GLB?

3D printing, feed an STL into your slicer to get G-code. 3D model delivery for the web (AR product viewers, WebXR scenes, embedded 3D widgets) and modern game-engine workflows. The most common reason to convert is compatibility, GLB works in places where STL doesn't, or vice versa.

How do I open a STL file in the first place?

Every 3D printing slicer, every CAD/3D tool (Blender, FreeCAD, Fusion 360, SolidWorks, Tinkercad). Free viewers: ViewSTL, MeshLab, online STL viewers.

Does this work offline?

Once the page is loaded, the conversion itself runs entirely offline. The first time you use a tool, your browser downloads the conversion library (a one-time cache). If you reload while offline, the page won't load, but you can install the site as a Progressive Web App for full offline use.

Can I convert multiple files at once?

Single file at a time for now. Batch conversion is on the roadmap, for now, drop one file, download the result, then convert the next.