When you're done creating a 3D model, hitting "Export" presents you with a confusing alphabet soup of extensions. STL? OBJ? GLB? Choosing the wrong one can mean losing your colors, breaking your mesh, or getting a file your printer can't read.
Here is the definitive guide to understanding the three most popular 3D file formats and when to use them.
1. STL (Stereolithography)
Best For: 3D Printing
The "Grandfather" of 3D formats. Simple, raw geometry.
If your goal is to physically print your model, STL is the industry standard. Every slicer software (Cura, PrusaSlicer) accepts it. However, it's "dumb" geometry—it knows nothing about color, texture, or materials. It simply lists triangles in 3D space.
- Pros: Universally supported by every 3D printer on the planet.
- Cons: No color, texture, or material support. Files can become huge.
2. OBJ (Wavefront Object)
Best For: Design & Editing
The versatile middle-ground. Supports textures.
OBJ is widely used when moving models between software like Blender, Maya, or Vextrude. Unlike STL, it can store UV maps (texture coordinates) and material groups. However, it usually requires a separate .mtl (material) file to define colors, which makes file management slightly annoying.
- Pros: Supports multi-color meshes and textures. Widely editable.
- Cons: Often requires two files (.obj + .mtl). Text format (slow to parse).
3. GLB / glTF
Best For: Web, AR, & VR
The "JPEG of 3D". Modern, compressed, and fast.
GLB is the future of 3D on the web. It packs geometry, textures, and even animations into a single, small binary file. If you want to show your 3D logo on a website (using Three.js or React Fiber) or in an AR app, this is the one you want.
- Pros: Tiny file size. Supports PBR (Physically Based Rendering) materials. Single file convenience.
- Cons: Harder to edit directly. Not supported by older legacy 3D printers.
Summary: Which one to pick?
| Goal | Format | Why? |
|---|---|---|
| 3D Printing | .STL | Printers understand it perfectly. |
| Web / AR / Games | .GLB | Fast loading & looks great. |
| Editing / Software | .OBJ | Easy to import into other tools. |
File Size and Performance
Beyond feature differences, file size has a direct impact on web performance and print workflow. Here is what to expect from each format in practice.
STL files store geometry as a list of triangle faces with no compression. A moderately complex model with 50,000 triangles produces a binary STL of roughly 2.5 MB. Simpler models like 3D text or basic logos typically stay under 500 KB. Always export binary STL rather than ASCII — the ASCII variant is five times larger with identical geometry.
OBJ is a plain-text format. The geometry is similar in size to ASCII STL, but the total asset footprint also includes the .mtl material library and any referenced image textures. A logo with a single solid color stays small, but a model with baked textures can easily become a 20+ MB asset bundle that must stay together as a folder.
GLB is the leanest option for web use. Binary encoding plus optional Draco mesh compression produces files 60–80% smaller than OBJ for identical geometry. A model that weighs 8 MB as OBJ is often under 1 MB as GLB. This matters enormously for page load speed, especially on mobile connections where every kilobyte counts toward Core Web Vitals scores.
Target sizes for web: Aim to keep individual GLB files under 1 MB for a smooth user experience. For 3D printing, file size is less critical since you upload to local slicer software that handles large files efficiently.
How to Convert Between Formats
Real-world projects rarely give you the luxury of choosing your starting format. Here are the most reliable conversion paths for each direction, whether you are converting for web, print, or software compatibility.
STL → GLB (print file to web)
Open the STL in Blender (free and open-source at blender.org). Go to File > Import > STL, add a material to the mesh in the Material Properties panel, then File > Export > glTF 2.0 and choose GLB as the output format. Since STL carries no color data, you must add materials in Blender before the export will include any visual information. This is the standard path for turning a print-ready asset into a web-ready one.
OBJ → GLB (design file to web)
Blender handles OBJ import natively and automatically reads the companion .mtl file if it is in the same folder. Import, verify the materials look correct in the Rendered viewport, then File > Export > glTF 2.0. For validation, the free online tool gltf.report can inspect and report on your GLB output, flagging oversized textures or unoptimized geometry before you deploy.
GLB → STL (web asset to print)
This is the trickiest direction because STL cannot store material data — all visual information is discarded. In Blender: import via File > Import > glTF 2.0, select all mesh objects with A, merge them with Ctrl+J to create a single printable solid, then File > Export > STL. For simple single-mesh models without complex rigging, online converters like Cloudconvert handle this reliably without needing to install software.
Using Vextrude for direct export
If you are creating assets from scratch in Vextrude — whether from text input or SVG uploads — all three formats are available from the same export panel. You choose the target format at download time, so no intermediate conversion is ever needed. This saves significant time compared to exporting to one format and then running a separate conversion step through Blender or an online tool.
Frequently Asked Questions
Can I 3D print a GLB file directly?
Not with standard slicers. Cura, PrusaSlicer, and Bambu Studio accept STL or 3MF files, not GLB. You need to convert GLB → STL first using Blender or an online converter, then import into your slicer software before sending to your printer.
My OBJ model appears solid grey in Three.js. What went wrong?
The .mtl material file is missing. OBJ splits geometry and materials into separate files — if you only provide the .obj file, Three.js has no material data to apply. The fix: switch to GLB for web use. GLB bundles geometry, materials, and textures into one self-contained file that Three.js loads with a single line.
What is the difference between glTF and GLB?
glTF is the JSON text format that references external binary buffers and texture files, which is useful when you need to swap textures without re-exporting. GLB is the binary container that packages the JSON, geometry buffers, and textures into one .glb file. For web delivery, GLB is almost always better — one file to upload, one file to cache, zero missing asset errors.
Which format is best for Augmented Reality?
GLB is the cross-platform standard for WebXR and the <model-viewer> web component. Apple’s native AR Quick Look uses USDZ for on-device AR, but for browser-based AR experiences targeting iOS, Android, and desktop simultaneously, GLB is the universal choice. Vextrude exports GLB directly from the same tool session.
Does STL support color or materials?
Standard binary STL stores only geometry — no color, no material, no texture. Some proprietary variants add per-triangle color data but lack universal slicer support. For multi-material or full-color 3D printing, use 3MF format instead, which natively handles color assignments, material properties, and print settings in a single file.