How it works
The checker examines the edges shared by STL triangles and counts open boundaries, non-manifold connections and disconnected shells.
What the results mean
A manifold mesh has a consistent surface around each edge. Open edges and non-manifold edges can confuse slicers; disconnected shells may be intentional but deserve review.
FAQ
What is a manifold mesh?
It is a mesh whose surface joins consistently without ambiguous edge connections.
Are disconnected shells always wrong?
No. Separate parts can be deliberate, but they may need separate printing decisions.
STL Watertight Checker · STL Quality Checker · All STL tools