STL to GLB Converter

Put a printable part on a website, in AR or in a three.js scene: STL to GLB at its real size, standing upright, in a file about a third the size of the STL.

  • Files stay on your device
  • Free, no sign-up
  • Units and up axis handled
  • Batch and .zip

Drop an STL file to convert

One file, many, or a .zip

In: STL · STEP · IGES · OBJ · 3MF · GLB · glTF · PLY · FBX · DAE · 3DS · AMF · VRML · ZIP

Converted on your device. Nothing is uploaded.

    How to convert STL to GLB

    1. Drop your STL files

      Drop one or more .stl files, binary or ASCII, or a .zip of them.

    2. Check the preview

      The model appears at the size and orientation it will have. Fix the file units, up axis or size under Size, units and orientation if needed.

    3. Choose GLB options

      No options needed: GLB is written in metres, Y up, with materials and textures embedded.

    4. Convert and download

      One file downloads straight away. A batch gives a download per file and one .zip of all of them.

    What carries over from STL to GLB

    Worked out from what each format can store and what this converter writes. Nothing is changed silently: the preview shows the size and orientation before you download.

    Geometry Every triangle is kept at full precision.
    Color STL has no color to carry. The GLB comes out uncolored.
    Units Converted from millimetres to metres, so it keeps its real size. A 50 mm part is written as 0.05.
    Orientation Turned from Z up to Y up, so it stands upright in web viewers and AR.
    Objects Each part stays a separate object or mesh.

    STL to GLB: what actually happens

    GLB is the web's 3D format and the only common one whose units and axes are fixed: metres, Y up. The converter turns the STL's millimetres into metres and its Z up into Y up, so a 50 mm part shows at 5 cm and upright in any glTF viewer, Android's Scene Viewer or a three.js page.

    STL repeats every corner for every triangle. The GLB shares them and leaves normals to the viewer (glTF readers shade such meshes flat, like the STL), which typically makes the file about a third of the STL's size. It gets a neutral grey material you can restyle in any editor.

    STL at a glance

    Stereolithography (Standard Triangle Language) · .stl

    Stores
    Loose triangles: three corners and a normal each, binary or ASCII
    Color
    None in the standard
    Units
    None written; slicers assume millimetres
    Up axis
    Z, the slicer convention
    File size
    50 bytes per triangle in binary, about 5 times that as ASCII
    Opens in
    Every slicer, CAD tool and 3D app

    Created by 3D Systems in 1987 for the first stereolithography printers, STL is still the format every slicer and print service accepts. It describes a surface as a list of independent triangles, with no shared vertices, units, colors or scene structure.

    Open STL files in the viewer

    GLB at a glance

    glTF 2.0 binary · .glb

    Stores
    Meshes, PBR materials, textures, animation and scenes in one binary file
    Color
    Full: textures, base colors and vertex colors
    Units
    Metres, fixed by the glTF spec
    Up axis
    Y, fixed by the spec
    File size
    Compact; Draco or Meshopt compression shrinks meshes 5 to 10 times
    Opens in
    Web viewers, Blender, Windows, Android Scene Viewer, Godot, Unity and Unreal importers

    glTF 2.0 is the Khronos Group's "JPEG of 3D", and GLB is its single-file binary form. It is what AI 3D generators, Sketchfab downloads and web apps hand out, and it is the only common format whose units (metres) and axes (Y up) are fixed by the spec.

    Open GLB files in the viewer

    Tips for STL to GLB

    For iPhone AR

    Apple's AR Quick Look wants USDZ: use STL to USDZ.

    Make it lighter

    For big scans, compress the GLB with Draco or Meshopt (for example with glTF-Transform) for another 5 to 10 times.

    Product pages

    Put the GLB in a <model-viewer> tag to show a print in 3D on your shop.

    STL to GLB FAQ

    Why is my GLB tiny in Blender?
    It isn't: glTF is in metres, so a 50 mm part is 0.05 m, its real size. Blender shows it at that size.

    Does the GLB keep flat facets?
    Yes. It has no normals, so viewers shade each triangle flat, the same look as the STL.

    Can I convert many STLs to GLB at once?
    Yes. Drop them all or a .zip and download every GLB in one .zip.

    Is the converter free? Are there limits?
    Free, with no sign-up, watermark or file count limit. Batches and files of a few hundred MB work on most laptops; the only limit is your device's memory.

    Are my files uploaded?
    No. Files are read and written by JavaScript and WebAssembly in your browser and never sent to PrintPal. The STEP and IGES reader is the only extra download, once, from a public CDN.