Open an STL file — view, measure and fix it
Drop the .stl and the model appears in 3D: drag to turn it, scroll to zoom. Its size, volume and weight are shown next to it, and holes or broken triangles are marked in red, with a Repair button one click away.
No server processing
No account
No daily limits
Saves model files for your slicer, never printer code. Opened and sliced in PrusaSlicer, OrcaSlicer, Bambu Studio and Cura.
What a .stl file is
STL is the file 3D printers have used since the 1980s: a list of triangles, each stored as its three corners, which together make the surface of the model. There are two kinds — binary, the usual one, and text (starting with the word “solid”) — and both open here. STL has no units, no colours and no notion of parts; slicers take its numbers as millimetres.
Because every triangle is stored on its own, nothing in an STL says which corners are shared, so a gap of a millionth of a millimetre is enough to make a hole. That is why downloaded models so often “have errors” in the slicer. Here you see where they are, repair them, and can save the model as 3MF, which keeps it exact.
What you can do here
Repair that keeps the shapeHoles are closed along their own edges and flipped triangles are turned, rather than rebuilding the model out of voxels — the surface stays where it was. Checked with PrusaSlicer on real broken models from Thingi10K.
Cuts that fit back togetherCut along any axis or at any angle and add round or square pegs — two or more, so the parts cannot twist — with a gap you choose for your printer. If the cut face is too narrow for the size you set, smaller pegs are used and you are told. Or holes in both parts and separate pins.
Solid geometry, not guessesCombine, subtract and cut run on Manifold, the open-source geometry library OpenSCAD and Blender use for the same job — the result is always a closed, printable solid.
Made for your slicer, not your printerIt saves model files, never printer code: temperatures, speeds and the G-code come from your own slicer and printer profile, and nothing here changes them. Saved files were opened and sliced in PrusaSlicer 2.9, OrcaSlicer 2.4, Bambu Studio 2.8 and Cura 5.13 — 3MF with painted colours, STL, OBJ and STEP (Cura reads no STEP on its own). As with any model, look at the slicer preview before you print.
Nothing to installWorks on Windows, Mac, Linux and a Chromebook, where Meshmixer and 3D Builder do not and where Bambu Studio cannot repair a model. The model never leaves your browser — nothing is uploaded.
Convert STL to something else
Questions
- Why does my STL look tiny?
- It was most likely drawn in inches: the numbers in the file are inches, read as millimetres. Under Mirror, scale press “Inches → mm”.
- Is the file uploaded?
- No. The model is read by your browser, on your computer; nothing is sent anywhere.
