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3DAI
Free · runs in your browser · no signup

Free Online STL Viewer

Check an STL before you print or share it. Open the file here to rotate and zoom around it, see its dimensions, triangle count, surface area and volume, and find out if the mesh is closed. The file never leaves your computer.

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How to use it

  1. 1

    Open an STL

    Drop a binary or ASCII .stl on the viewer or click to browse.

  2. 2

    Look around

    Drag to rotate, scroll to zoom, right-drag to pan. Use the front, side and top buttons for straight views and Wireframe to see the triangles.

  3. 3

    Read the numbers

    Size, surface area and volume, in mm or inches. Volume shows only for closed meshes.

  4. 4

    Check printability

    The watertight line counts open and non-manifold edges, the usual cause of slicing errors.

What to know before you convert

  • Only STL files open here. To view a GLB or OBJ as it will print, use the GLB to STL or OBJ to STL page, which show the same preview.
  • The model is shown in one grey colour. Colour data in some binary STLs is not displayed.
  • Units are assumed to be millimetres, as slicers do. STL itself has no units.
  • The viewer does not repair or edit meshes. The watertight check is skipped above 3 million triangles to keep the page responsive.
  • Very large files depend on your device memory. 100 MB is the upper limit.

Don't have a model?

Generate one from a sketch, image or text. Our AI generators give you a 3D model with an STL download for printing. They use credits; this converter does not.

Sketch to STL →Draw it, get a printable model.Image to STL →One photo of an object.Text to STL →Describe it in a sentence.

Frequently Asked Questions

Drop it on the viewer above. It runs in any modern browser with WebGL on Windows, macOS, Linux, ChromeOS and most phones, with nothing to install.
From the triangles themselves, by summing signed tetrahedra. That is only correct when the mesh is closed, so the viewer hides volume when it finds open edges. Slicers give a different number for filament because of infill and walls.
Some edges belong to only one triangle (a hole) or to more than two (non-manifold). Slicers may fill these in, print them oddly or refuse the file. Fix them in your modelling tool or with a mesh repair tool before printing.
STL stores bare numbers. The viewer reads them as millimetres, as slicers do. A model saved in metres or inches will look too small or too big; convert or scale it before printing.
Yes. The buttons next to the viewer save the model as a binary STL (handy for shrinking a large ASCII STL) or as an OBJ. For scale and axis options, use the STL to OBJ converter.
No. The page reads the file and converts it inside your browser with the open-source three.js library. Nothing is sent to our servers, there is no account, and no credits are used. Closing the tab discards everything.