Online STL viewer
Open an STL, OBJ, 3MF, PLY or GLB file and turn it around in 3D, right in your browser. See its exact size, how many triangles it has, whether it is watertight for printing, its volume and roughly how much filament it needs. Then save it as STL, 3MF or OBJ.
Open a 3D model
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- Size
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- Mesh
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- Watertight
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- Volume
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- Surface
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- Filament
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More formats
How to view an STL file online
Drop the file in the box above, or click to pick it. It opens in a second or two, even with millions of triangles.
Turn it around: drag to orbit, scroll or pinch to zoom, right-drag or two fingers to pan. Tick Show triangles to see the mesh.
Read the facts under the view: size in millimetres, triangle count, whether it is watertight, volume, surface area and filament.
Wrong size or lying on its side? Change File units, type a Scale, or tick Y is up for models from Blender, Maya and most 3D sites.
Save it as STL, 3MF or OBJ, or edit it in FlatCad 3D.
What the checks tell you
- Size: the box the model fits in, after it is placed on the bed. Compare it with your printer's build volume.
- Watertight: "Yes" means a closed solid that any slicer will read cleanly. "No" counts the edges that are open (a hole) or shared by more than two faces.
- Volume and filament: the solid volume, and an estimate for a normal print at 15% infill.
Need a different format? STL to OBJ, OBJ to STL and 3MF to STL use the same tool. Want to change the part? Edit an STL online.
Open FlatCad 3D, free, no signup
Questions
Which files can it open?
STL (binary and ASCII), OBJ (with its .mtl), 3MF, PLY, GLB and glTF (with its .bin). Pick the extra files together with the model, or drop them all at once.
What does watertight mean?
A 3D printer needs a closed surface: every edge shared by exactly two triangles, like a balloon with no tears. If the model has holes, slicers may fill them oddly or skip parts. Close small holes repairs simple gaps; a model with many open edges should be fixed in the tool that made it.
Why is my model the wrong size?
STL and OBJ files store bare numbers without units. The tool reads the units when the file says (3MF, glTF, or a note in the header) and otherwise guesses from the size; if it guessed wrong, pick File units, or type a Scale. Downloads are always in millimetres.
How accurate is the filament estimate?
It assumes about 0.8 mm of walls and skins and 15% infill, in PLA. Your slicer gives the exact figure for your settings; this is for a quick idea of cost before you slice.
Can I change the model?
Press Edit in FlatCad 3D: the model opens in a free 3D CAD app where you can drill holes, add text, cut it, or join it to other shapes, then export a new STL.
Is my file uploaded?
No. The model is read and converted in your browser; it never leaves your computer, so private or client parts stay private.
How big a file can it open?
Files up to about 250 MB, several million triangles, in a desktop browser. Phones manage smaller files.