3D File Formats Explained: Which Should You Use?

STL is the oldest and most universal 3D printing format. It describes a model as a plain list of triangles - nothing else. No colors, no materials, no units, no object names. That simplicity is exactly why every slicer, CAD tool, and print service on earth accepts it.

An STL file stores each triangle as three corner points plus a facet normal, either as compact binary (the common case) or human-readable ASCII. Because the format carries no unit information, almost every tool assumes millimeters. When a file needs to work absolutely anywhere, STL is still the safe answer.

3MF is the modern 3D-printing format designed to fix STL's gaps. A single .3mf file can hold multiple objects with names, colors, materials, real units, and even slicer settings like plate layout - which is why modern slicers such as Bambu Studio and PrusaSlicer use it as their native project format.

Under the hood a 3MF file is a ZIP archive with an XML model inside, so it stays compact while carrying far more information than STL. The catch: plenty of older slicers, CAD importers, mesh repair tools, and model marketplaces still only accept STL - which is exactly when you convert.

OBJ is the plain-text workhorse of 3D interchange. It stores vertices, faces, UV coordinates, and normals in a human-readable file, with materials referenced from a companion .mtl file. Practically every 3D application of the last 30 years can read it.

Because OBJ splits materials and textures into separate files, a bare .obj carries geometry and UVs but shows up untextured unless the .mtl and texture images travel with it. It has no units, no rigging, and no animation - which keeps it simple and universally compatible.

GLB is the binary form of glTF, often called "the JPEG of 3D". One file packs the full scene: meshes, PBR materials, embedded textures, animations, and a real unit scale (meters). It is the standard for 3D on the web and the default output of most AI 3D generators.

Because everything is embedded in a single binary file, GLB transfers cleanly between tools with nothing lost in transit. glTF/GLB is an open Khronos standard, loads fast, and is supported by every modern engine, DCC tool, and web viewer.

glTF is the JSON flavor of the same Khronos standard behind GLB. The scene description is human-readable JSON, typically pointing at external binary buffers and texture images. Same capabilities as GLB - PBR materials, animations, real units - in a multi-file layout.

The multi-file layout makes .gltf convenient to inspect and edit but fragile to share: if the .bin or textures go missing, the file breaks. For distribution, most pipelines pack glTF into single-file GLB - the conversion this fleet does in one click.

PLY was designed at Stanford to store scanned 3D data. Its superpower is per-vertex properties - most importantly vertex colors - which makes it the default output of 3D scanners, photogrammetry pipelines, and Gaussian-splatting tools.

PLY stores flexible per-vertex data (position, color, normal, confidence) plus faces. It has no materials, textures, or units. Scan data usually moves through PLY on its way to a printable STL or a web-ready GLB.

FBX is Autodesk's proprietary scene format and the long-standing standard for moving rigged, animated characters between DCC tools and game engines. Skeletons, skinning, blend shapes, and animation clips all travel inside one file.

Because the format is closed, no official browser tooling exists - this fleet writes FBX through assimp's open-source FBX writer running as WebAssembly, right in your browser. Static geometry with UVs is the reliable path; rigs and animation clips need a DCC-tool export.

COLLADA (.dae) is an XML-based interchange format that predates glTF. It can carry full scenes with materials, rigs, and animations, and remains common in SketchUp exports, older asset marketplaces, and legacy game pipelines.

As an XML format, .dae files are verbose and slow to parse, and tool support has been fading in favor of glTF/GLB and FBX. It survives on two ecosystems: SketchUp imports COLLADA natively (most other mesh formats need Pro or plugins), and Second Life accepts mesh uploads only as .dae - so files move both ways, legacy assets out and fresh conversions in.

STEP is the engineering world's exchange format: an ISO standard that describes parts as exact mathematical solids (B-rep) rather than triangle meshes. CAD packages, CNC shops, and manufacturers all speak STEP - it is how precise parts travel between engineering tools.

Because STEP stores exact surfaces with real units, converting it to a mesh format means tessellation - sampling the math into triangles (this converter uses OpenCascade, the same kernel FreeCAD builds on). Going the other way, a mesh can only become a faceted STEP: triangles wrapped as B-rep, valid in every CAD tool but not parametrically editable.

USDZ is Apple's AR format: Pixar's Universal Scene Description packed into a single file that iPhones and iPads open natively in AR Quick Look - no app required. E-commerce product previews on Apple devices run on USDZ.

USDZ shines on Apple platforms and almost nowhere else, so the common workflows are converting a GLB into USDZ to ship an AR preview, or unpacking a USDZ back into GLB/OBJ to edit it in standard tools.