Do my files get uploaded?

No. Everything runs in your browser. The file never leaves your computer, so it works for client files and unreleased designs too.

Badly broken scans, big missing chunks, and parts that cut through each other. Those need a remesher (Meshmixer, Blender's 3D Print Toolbox, or your slicer's built-in repair).

What does watertight mean?

Every edge is shared by exactly two triangles, so the surface has no gaps. Slicers need that to know what's inside the part and what's outside.

Will it change my model's shape?

Only where it fills a hole. A hole gets closed with a flat-ish patch. Everything else stays where it was.

All tools / STL repair

Fix an STL file

Your slicer says the model has errors? Drop it here. We close small holes, fix flipped faces and clean out junk triangles, then show you what changed.

Good to know

GuideNon-manifold edges, explainedA non-manifold edge is a spot where the mesh couldn't exist as a real, solid object.

What your slicer's warnings mean

Warning	What it is	Fixed here?
Open edges / holes	Gaps in the surface, so there's no clear inside and outside	Yes, small holes are closed
Flipped or inverted normals	Some faces point inward, so the slicer thinks they're inside out	Yes
Duplicate or zero-area faces	Leftover triangles that sit on top of each other or have no size	Yes, they're removed
Non-manifold edges	One edge shared by three or more faces, often where two parts touch	Shown in red, not rebuilt
Self-intersecting faces	Parts of the mesh pass through each other	No, needs a remesher

Holes and flipped faces are the common ones, and those are what this tool fixes. Tangled meshes need heavier software.

If it's still broken

Try your slicer's own repair. Bambu Studio and PrusaSlicer both have one; in both it only runs on Windows.
In Blender, select the mesh, press Tab, then Select → Select All by Trait → Non Manifold to see the trouble spots.
For 3D scans, a remesh (rebuilding the surface from scratch) usually works better than patching.

How it works

1Drop the STL (or 3MF, OBJ) in the box.
2Read the check: open edges, bad edges, and whether it's watertight.
3Click Repair, look at the before and after, and download the fixed STL.

Questions people ask

Checked October 2026

Do my files get uploaded?: No. Everything runs in your browser. The file never leaves your computer, so it works for client files and unreleased designs too.
What can't it fix?: Badly broken scans, big missing chunks, and parts that cut through each other. Those need a remesher (Meshmixer, Blender's 3D Print Toolbox, or your slicer's built-in repair).
What does watertight mean?: Every edge is shared by exactly two triangles, so the surface has no gaps. Slicers need that to know what's inside the part and what's outside.
Will it change my model's shape?: Only where it fills a hole. A hole gets closed with a flat-ish patch. Everything else stays where it was.

Other tools you might need

STLPalTool

Edit

Free · in your browser · no upload

STL editorResize, rotate, mirror and combine STL files right here

STLPalViewer

.STL

Free · in your browser · no upload

STL viewerOpen any STL to look it over before you print

STLPalConverter

3MF→STL

Free · in your browser · no upload

3MF to STLGot a 3MF from MakerWorld or Printables but your tool wants STL? Drop it here and get an STL back at the right size

STLPalConverter

OBJ→STL

Free · in your browser · no upload

OBJ to STLOBJ files from Blender or a game usually lie on their back and come in odd sizes