Degenerate faces and duplicate faces can often be removed safely after validation.
Fix STL file
Find what is wrong with a STL file before you print it.
Use the checker to separate safe automatic fixes from geometry that needs manual modeling or slicer review.
Open boundaries and non-manifold edges are highlighted with severity so you know where the model may be non-watertight.
Normal direction mismatches are reported separately from topology issues because they have different repair risk.
The report explains skipped repairs instead of hiding failures behind a generic repaired download.