View an STL file in your browser
STL is the universal 3D-printing format — the mesh of triangles every slicer and CAD tool reads. Sometimes you just need to look at one: check it's the right model, see how big it is, count the triangles, or confirm a download isn't broken before you fire up a slicer. This viewer opens it in one drag, with no install and no account.
Everything happens in your browser. The file is read and rendered on your machine, and nothing is sent anywhere — handy for client work, paid models, or anything you'd rather not hand to a random web service. Drag to rotate, scroll to zoom, right-click-drag to pan, and hit Reset to re-frame if the model drifts off-screen.
STL, OBJ and 3MF — all in one viewer
As well as STL (binary or ASCII), this tool opens OBJ and 3MF files. For each one it shows the geometry plus an info row: triangle count, vertex count, and the bounding-box dimensions in millimetres — enough to sanity-check a model's size and complexity before printing. A 3MF with several plates or parts is merged into one mesh for the preview.
What the viewer shows — and what it doesn't
It renders the mesh in a neutral grey, like an unpainted print, so you can read the shape clearly. It doesn't show per-object colour or multi-material paint stored in a 3MF, and it doesn't edit the mesh. If colour is the point — multi-filament or AMS printing — don't stop at viewing: open the model in Layerpaint, paint per-region colours, and export a Standard 3MF your slicer prints in real filament. Need a different format? Use the 3MF ⇄ STL converter.