STL file viewer
Open an STL file and look at it properly: turn it around, switch on the wireframe, read its real size, and find out whether it has holes in it. The file is read by your browser and never leaves your computer.
Drag a 3D file here, or.
Opens STL, OBJ, PLY, OFF, glTF, GLB, 3MF, COLLADA, FBX, STEP, IGES, BREP, Rhino 3DM, PNG, JPEG, SVG, DXF, ZIP and G-code.
The file is read on your own computer. It is never uploaded.
What this STL file viewer tells you
Most viewers draw the model and stop there. This one measures it first, because the questions people actually have about an STL are about size and about whether it will print.
Width, depth and height are the real dimensions of the part. An STL does not record its own units, so the numbers are shown in millimetres, which is what every slicer assumes. If your part is meant to be 60 mm across and the viewer says 0.06, the file was written in metres.
Open edges is the number that matters before you print. A solid object has none: every edge is shared by exactly two triangles, so the surface closes completely. An edge with only one triangle is the border of a hole. A slicer faced with holes has to guess where the inside is, and the guess is often wrong.
Volume is only shown when the model is closed, because it only means anything when the model is closed. A figure quoted for a mesh with holes would be a number with no meaning behind it.
The model is repaired before you see it
An STL file stores every triangle separately, with no record of which ones touch. Before drawing anything, this viewer joins the points that sit in the same place, works out which triangles are neighbours, and makes them agree about which side faces out. Triangles with no area are removed.
That is why a file that looks wrong in other viewers — patches of black, faces that vanish as you turn it — often looks right here. Nothing about the shape is changed. Only the bookkeeping is fixed.
Reading the view
Drag to turn the model. Scroll to zoom. Drag with the right button, or with two fingers, to slide it across. Wireframe shows the triangles themselves, which is the quickest way to see whether a model is dense enough for what you want to do with it. Fit view puts the whole model back in frame.
The coloured marker in the corner is the axis indicator: red is X, green is Y, blue is Z. It shows which way the file is oriented, which is what tells you whether a model will arrive upright in another program.
Questions
- Do I need to install anything to view an STL file?
- No. This STL file viewer runs inside your web browser. There is nothing to download and no account to make.
- Is my STL file uploaded to a server?
- No. The file is read by your own browser and stays on your computer. That matters if the part is confidential, and it is why the viewer works when you have no internet connection after the page has loaded.
- How big a file can it open?
- Files up to about 250 MB. A 50 MB STL, which is roughly a million triangles, opens in a few seconds and the page stays responsive while it works.
- What do the numbers under the model mean?
- Width, depth and height are the size of the box the model fits inside. Triangles and points describe how detailed it is. Open edges count the places where the surface has a hole, which is what stops a model printing as a solid.
- Which other files can it open?
- OBJ, PLY, OFF, glTF and GLB as well as STL. Drag any of them onto the page.
Convert the file instead
Where to go next
Now do something about it
- Gridfinity generatorBins and baseplates, any size, built in the browser
- Turn text into an STLType a word and print it, without drawing anything
- Turn an image into an STLA photo or a logo, turned into something you can print
- Lithophane generatorA photo printed as thickness, lit from behind
- Repair an STL that will not sliceClose the holes and separate the bad edges so a slicer accepts it
- Reduce the size of an STL fileFewer triangles, the same shape, a much smaller file
- Check whether an STL is ready to printFind out what is wrong with a model before you print it
- 3D printing cost calculatorThe real cost of a print, and whether to print it or order it