STL File Viewer
Upload an STL model, rotate it in 3D, and read dimensions, volume, and weight instantly
This free online STL viewer lets you open and inspect any STL file directly in your browser — no CAD software, no registration, and no upload to a server. Drop in a model exported from SolidWorks, Fusion 360, Inventor, FreeCAD, Blender, or any 3D scanner, and it renders instantly with full 3D orbit, zoom, and pan controls.
Beyond viewing, the tool measures your model: it reports the exact bounding-box dimensions, total surface area, enclosed volume, and triangle count. Because STL files carry no unit information, you can switch between millimeters and inches and all readings update instantly.
For metalworkers, the built-in weight estimate is the key feature: pick a material — steel, stainless, aluminum, brass, copper, or titanium — and the viewer multiplies the model volume by the alloy density to predict the part weight before you machine, cast, or 3D-print it in metal. Combine it with our weight calculator for stock material and our LME price feed to estimate raw material cost.
Frequently Asked Questions
Is my STL file uploaded to a server?
No. The viewer runs 100% in your browser using WebGL. The file is read locally in memory and never transmitted anywhere, so proprietary designs stay on your computer.
Which STL formats are supported?
Both binary and ASCII STL files are supported and detected automatically. Binary STL is the compact format most CAD packages export by default; ASCII STL is the human-readable variant.
How is the volume calculated?
The viewer sums signed tetrahedron volumes over every triangle in the mesh (the divergence theorem). For a watertight (closed, manifold) mesh this gives the exact enclosed volume; for meshes with holes the result is approximate.
How accurate is the weight estimate?
Weight = volume × density. The volume is exact for watertight meshes, and standard alloy densities are used (e.g. steel 7,850 kg/m³, aluminum 2,700 kg/m³). Real parts may differ slightly due to alloy composition, porosity, or machining tolerances.
Why do the dimensions look wrong?
STL files store bare numbers without units. Most CAD software exports in millimeters, which is the default here. If your file was made in inches, switch the file-units selector to inches and all measurements rescale.