How to open an STL file online
- Drop the .stl file into the box above or click Choose file.
- Drag to rotate, scroll or pinch to zoom, right-drag or two-finger drag to pan.
- Use the buttons for front / top / side views, wireframe and screenshots.
- Pick an output format on the right to convert and download.
What the viewer shows
- Dimensions of the bounding box (X × Y × Z) in millimetres.
- Triangle count and number of parts.
- Surface area and volume (for closed meshes).
- Watertight check – whether the mesh is closed, which matters for 3D printing.
About STL files
STL (Stereolithography) was created by 3D Systems in 1987 for its stereolithography printers. It describes only the surface of a model as a list of triangles, without colour, materials or units. It is the default file for 3D printing and the format almost every slicer (Cura, PrusaSlicer, Bambu Studio, Chitubox) opens.
Desktop programs that open STL
- PrusaSlicer, Cura, Bambu Studio and other slicers
- Blender
- MeshLab
- FreeCAD
- Windows 3D Viewer / 3D Builder
Frequently asked questions
Is the viewer free?
Yes – viewing is free and unlimited, without an account. Converting and downloading is free for up to 3 files a day; Pro removes the limit.
Is my file uploaded?
No. The file is read by your browser and rendered with WebGL on your device. It is never sent to a server.
How do I check if my STL is printable?
After opening, look at "Watertight". "Yes" means every edge is shared by exactly two triangles – the mesh is closed and slicers will treat it as a solid. Open edges indicate holes that may cause missing layers.
Can I measure the model?
The panel shows the bounding-box size in millimetres, the surface area and – for closed meshes – the volume in cm³, which you can use to estimate material use.
Does it work on iPhone and Android?
Yes. Open the page in Safari or Chrome, tap Choose file and pick the model from Files or Downloads.