Free STL Viewer Online
Drop an STL file below to turn it, zoom in, and check its triangle count and size. It all happens in your browser, so your file is never uploaded.
Your files never leave your browser. Nothing is uploaded.
What is an STL file?
STL is the plain format of 3D printing. It stores a model as a list of triangles and nothing else: no colors, no textures, and no unit. Slicing programs and CAD tools all read it.
CAD apps such as Fusion and Onshape export STL, and so does Blender. Model sites such as Thingiverse and Printables list printable models as STL.
Both the binary and the text form of STL open here.
How to view an STL file
Drop the STL file on the viewer above, or choose it from your device. The model opens in a moment and fills the frame.
Drag to orbit around your STL model, and scroll or pinch to zoom. The Corner, Front, Side, and Top buttons jump to a standard view.
An STL has no colors, so Shaded and Clay look much alike. The viewer stands STL models on the Z axis, the way CAD tools and slicers do. If a part lies on its side, press Turn upright to use Y instead.
Checking a part before you print
Look at the size first. Slicers read STL numbers as millimeters, so a box that reads 40 × 40 × 10 should be 40 mm wide. A part that reads 0.04 or 40000 was probably exported in the wrong unit.
The triangle count tells you how fine the surface is. A smooth curve needs many small triangles, and a coarse export shows flat facets on round parts. A scanned object can have hundreds of thousands of triangles. Millions can make a slicer slow.
This viewer shows the shape. It does not test whether the model is closed or printable. Your slicer can check that.
What the numbers mean
The triangle count shows how detailed the surface is. More triangles mean more work for the device that draws the model, so a model that turns slowly may need a lighter export.
The size is the width, height, and depth of the box around the model. For an STL the size is in the file's own numbers. Slicers read them as millimeters, so 40 × 40 × 10 means a part 40 mm wide.
Fixing common problems
If the model lies on its side, change the up direction to Y.
A model with holes or flipped faces was already broken when it was exported. Repair it with your slicer's repair tool before you print.
Files over 150 MB are not opened. Export just the part you need.
If you see a message about 3D, your browser may have WebGL turned off. Try another browser, or turn on hardware acceleration in the browser settings.
Your file stays on your device
The viewer reads your STL file in the browser. Nothing is uploaded, and the page does not load anything the file points to. The page counts a visit like any other page, but it never sees the file's name or contents.
From a viewer to a finished render
A viewer shows you the model. A render shows you how it could look built. The Inkfinish studio opens STL files too, lets you pick the angle, and turns that view into a finished image from a short description of materials and light.
Questions
Is this STL viewer free, and is my file uploaded?
It is free, and you do not need an account. The file is read in your browser and never uploaded, so it stays on your device.
What unit is an STL file in?
An STL does not say. Slicers and print services read its numbers as millimeters, so most files are made that way. The viewer shows the size as plain numbers without a unit.
Can I see colors in an STL?
No. The format has no place for colors or textures, so every STL looks plain. A 3MF file can keep colors.
Does this viewer check whether my model can be printed?
No. It shows the shape, the triangle count, and the size. It does not test whether the surface is closed. Use your slicer's checks for that.
How large a file can I open?
Files up to 150 MB. A very large model may open slowly on a phone or an older computer, so export only the part you need if it struggles.
What does the triangle count tell me?
It is the number of triangles that make up the model's surfaces. A higher count means more detail and more work for the device that draws it.
More free tools
- Free 3D Model Viewer OnlineOpen a 3D model in your browser: GLB, glTF, OBJ, FBX, STL, 3MF, or DAE. Turn it, zoom in, and check its size and detail. Free, with no upload.Free, in your browser
- Free STL to GLB ConverterConvert an STL file to GLB in your browser to share a printable part on the web or in AR. Free, with no upload and no sign-up.Free, in your browser
- Free STL to 3MF ConverterConvert an STL file to 3MF in your browser. Joins matching corners and states the unit. Free, with no upload and no sign-up.Free, in your browser
- Free STL to OBJ ConverterConvert an STL file to OBJ in your browser to open a printable part in modeling and render apps. Free, with no upload and no sign-up.Free, in your browser
- Free 3MF Viewer OnlineOpen a 3MF file in your browser. Turn it, zoom in, and check the triangle count and size. Free, with no upload and no sign-up.Free, in your browser
- Free GLB to STL ConverterConvert a GLB file to STL for 3D printing in your browser. Scaled to millimeters and stood upright for your slicer. Free, with no upload.Free, in your browser
Make it a finished render
Open the studio and add your STL file. The studio opens GLB, glTF, OBJ, FBX, STL, 3MF, or DAE files. You pick the angle and describe the finish, and Inkfinish renders that view as a finished image.
Try 3 renders free, no sign-up needed: watermarked, at standard size.
Updated October 2026. Open-source licenses