Repair STL Online

Slicer complaining about non-manifold edges or holes? Upload the STL — we fix winding, normals, duplicates and small holes, and show you a before/after watertight report.

Before/after reportFixes normals & holesFree ≤25 MBNo sign-up

What gets fixed

Honest limits: catastrophic damage (missing whole regions, self-intersecting shells) needs manual work in Meshmixer or Blender — our report tells you if the mesh still isn't watertight after repair, so you're never guessing.

Frequently asked questions

Why does my slicer say the STL is not manifold?
Every edge in a printable mesh must join exactly two faces. Holes, duplicated faces or unwelded vertices break that rule. Upload the file — the fixes above solve most cases, and the report shows watertight status before and after.
Will repair change my model's shape?
Only minimally: filled holes get flat caps, duplicates are removed. Overall geometry and dimensions stay as-is — the report includes face counts so you can verify.
Is this converter free?
Yes — up to 10 conversions a day and files up to 25 MB, no account needed. Larger files (up to 60 MB) and high-detail STEP output use credits ($9 for 20). Everything runs server-side on real geometry kernels, and failed jobs auto-refund.
What happens to my files?
Files are uploaded only to run your conversion and stored briefly so you can download the result. We don't share them, mine them or train on them. See our privacy policy.

Related converters

STL → GLBSTL → STEPSTL → OBJ3MF → STLOBJ → STLPLY → STL

Every converter runs the same geometry engine — see all 20 conversions.