How to smooth an STL and increase its resolution
- 1
Drop your STL
Binary or ASCII STL up to 300,000 triangles. It is read on your device and never uploaded.
- 2
Pick levels and sharp edges
Each level makes 4 times as many triangles (up to 1.5 million). Keep sharp edges on for parts with flat faces and corners; lower the angle to keep more edges crisp.
- 3
Compare and download
Check the side-by-side preview with the triangles shown, then download the smoothed model as a binary STL or a 3MF for your slicer.
Smooth curves vs split only
| Smooth curves | Split only | |
|---|---|---|
| What it does | Splits each triangle into 4 and moves points onto a smooth curve (Loop subdivision) | Splits each triangle into 4 at the edge midpoints; the shape stays exactly the same |
| Facets | Gone after 2-3 levels on most models | Still there unless you add extra smoothing passes |
| Size | Very coarse shapes get a little smaller (the corners round in) | Unchanged; extra passes keep the size too (Taubin smoothing) |
| Sharp edges | Kept when the faces meet at more than your angle | Kept the same way |
| Best for | Low-poly and faceted curves: cylinders, spheres, organic and AI models | More triangles for sculpting or deforming, or gentle smoothing that keeps the size |
Why your STL looks faceted, and why smooth shading does not fix it
An STL is only a list of flat triangles. When a CAD program or an AI model exports a curve with too few of them, every flat triangle shows up in the print as a facet or a ridge. Smooth shading in Blender or a viewer only changes how light falls on the screen; the file still holds the same flat triangles, and the slicer prints those.
To really smooth the file you need more triangles placed on the curve. That is what this tool does: it subdivides the mesh and smooths the new points, so the curve is made of many small triangles instead of a few big ones. If you still have the original CAD file, exporting it again at a finer tolerance is the most exact fix; this page is for when the STL is all you have.
How the smoothing works
Smooth curves uses Loop subdivision (Charles Loop, 1987): every triangle becomes 4, each new point on an edge is a weighted mix of the nearby points, and each old point moves towards its neighbours. After a few levels the surface converges to a smooth curve. Edges where the faces turn more than your sharp-edge angle are treated as creases (Hoppe et al., 1994): points on a crease only follow the crease, and corners where 3 or more creases meet do not move at all, so a cube stays a cube.
Extra smoothing passes use Taubin smoothing (Gabriel Taubin, 1995), which alternates a shrinking step and a slightly bigger growing step, so bumps flatten without the model shrinking the way plain averaging does. The code was written for this page from those papers; it runs in a background thread in your browser and keeps the mesh watertight when your file is watertight.
Got a low-poly AI model? Smooth it, then texture it
Make the model, smooth it here, then paint it, or fix and slim the file for printing.
Image to 3D model
Turn a photo into a 3D model with AI, then smooth it here before you print.
AI 3D texturing
Paint your smoothed model with AI textures from a text prompt or an image.
STL repair
Close holes and fix flipped triangles first, so the smoothed file is watertight.
Reduce STL file size
Too many triangles after smoothing? Bring the count back down while keeping the shape.