Online STL Viewer

How to use the STL viewer

1. Open your file. Click Open a file, or drop it anywhere on the page. STL, OBJ, GLB, glTF, 3MF and PLY all work. A .gltf that keeps its data in a separate .bin needs both files selected together.
2. Turn and zoom. Drag to turn, scroll or pinch to zoom, and right-drag or Shift-drag to pan. With the view selected, the arrow keys turn it and + and − zoom. Top, Front and Side jump to a straight-on view.
3. Check the size. The size is shown in millimetres. If an STL looks 10 or 25.4 times too small, it was probably drawn in centimetres or inches: change File units.
4. Stand it the right way up. glTF files are Y-up, so they are turned to Z-up, the way printers work. If a model lies on its side, use the 90° turn buttons. Place on the bed puts its lowest point at z = 0.
5. Look for problems. The check lists open and non-manifold edges. Choose Problem edges to see where they are on the model.
6. Save as STL if you need one. Download STL writes a binary STL in millimetres with your units, turns and placement applied.

What the checks mean

The checks run on the exact coordinates that go into the downloaded STL. Two corners count as the same point when they match to 0.0001 mm, the same rule the MakerJig generators use before they let you download.

• Open edges belong to only one face, or to faces that don't line up. They are holes, so the model is not watertight, and the slicer has to guess what is inside. Small gaps are usually repaired by the slicer; big ones show up as missing walls or layers.
• Non-manifold edges are shared by three or more faces, for example two boxes touching along one edge, or a wall inside a solid. Slicers often cope, but they can cause strange slices.
• Zero-area triangles have two corners in the same place. They are usually harmless, but a lot of them suggests a messy export.
• Inside out means the mesh is closed but its faces point inwards, so the volume comes out negative. Most slicers fix this on their own.
• Separate parts counts the pieces that don't touch. Several is normal for a plate of objects; for a single part it can mean loose fragments.
• Volume and weight are only measured when the mesh is closed and manifold, because an open surface has no inside. The weight assumes a solid print, so it is an upper limit.

Convert GLB, OBJ or 3MF to STL

Because the viewer can save whatever it opens, it also works as a GLB to STL, OBJ to STL, 3MF to STL and PLY to STL converter. Only the shape is kept: colours, materials, textures and animation are dropped, because STL can't store them. The mesh is not repaired, so the check above tells you what the STL will be like. glTF files are scaled from metres to millimetres; check the size before you print.