STL file format (.stl)

STL (Stereolithography / Standard Triangle Language)

What is a STL file?

STL is the de-facto standard for 3D printing. It describes a model purely as a mesh of triangles — no color, no units, no assembly structure — which makes it simple, universally supported, and the required input for virtually every slicer, from PrusaSlicer and Cura to resin-printer tools.

Accepted by every slicer and 3D printer workflow
Simple, robust and universally supported
Binary variant keeps files compact

Best for: 3D printing and rapid prototyping.

View STL files online

Open .stl files in the free online STL viewer — assembly tree, section views and display modes, entirely in your browser.

How to open a STL file

Open the online STL viewer. It runs in your browser, so there is no software to install and no account to create.
Drop your .stl file in. The file is parsed locally and never uploaded. Inspect it with the assembly tree, section views and display modes.
Convert it if you need another format. Press Convert to turn STL into OBJ, then download the result straight from your browser.

Convert STL to other formats

STL to OBJ STL to PLY STL to GLB STL to glTF STL to 3MF STL to OFF STL to USDZ

Convert other formats to STL

STEP to STL IGES to STL BREP to STL OBJ to STL PLY to STL GLB to STL glTF to STL 3MF to STL COLLADA to STL AMF to STL FBX to STL 3DS to STL OFF to STL LAS to STL PCD to STL XYZ to STL PTS to STL

Frequently asked questions

How do I open a .stl file?

Drop it into the free online STL viewer on this site — it renders in your browser with an assembly tree and section views, and the file is never uploaded. No software install needed.

Does STL store units and colors?

Units: no — unitless numbers. Colors/materials: no. Geometry is stored as triangle mesh.

How do I convert STL to OBJ?

Use the free STL to OBJ converter: drop the file, press Convert, download. Everything runs locally in your browser — no upload, no signup.

What is STL best used for?

3D printing and rapid prototyping.

What important information is missing from STL?

STL is only a triangle surface with unitless coordinates. It has no standard part names, assembly hierarchy, colors, materials or editable CAD features, so keep the source model as well.

Can STL store animation?

No. STL is used for 3d printing, and its format does not carry animation tracks.