How to repair an STL
- Drop your STL (or OBJ, 3MF, PLY) into the box above. The repair runs automatically.
- Check the panel: Watertight should now say Yes, and the status line tells you how many holes were filled.
- Download the repaired STL – or choose 3MF for a smaller file.
What the repair does
- Welds vertices that sit on top of each other, so neighbouring triangles really connect.
- Removes degenerate and duplicate triangles (zero area or listed twice).
- Makes the winding consistent so every normal points outwards – slicers then know what is inside and outside.
- Fills holes by closing each open boundary loop with a fan of triangles.
What it can't fix
Self-intersecting shells, very thin walls and models with large missing areas need a modelling tool (Meshmixer, Blender 3D Print Toolbox, or your CAD program). For a step-by-step guide see how to fix non-manifold STL files.
Frequently asked questions
Why does my slicer say the model has errors?
Usually the mesh has holes (open edges) or inconsistent normals. Both make the inside/outside ambiguous, which leads to missing layers. This tool fixes both.
Is it free?
Yes – up to 3 downloads a day are free, with no sign-up or watermark. Pro (free for 7 days) makes it unlimited.
Is my file uploaded?
No. The file is processed in your browser and never leaves your device.