Free mesh preflight

STL Quality Checker

Run one broad mesh check to see which supported findings exist before you edit the STL. The report separates boundaries, over-shared edges, exact duplicates, degenerate faces and winding findings; a clean result is not a complete slicer or print test.

Choose your file

Select a non-empty .stl file up to 25 MiB. Pressing Check explicitly uploads it for server analysis; local viewing does not. Review the privacy policy before submitting private geometry.

Choose STL file

Select a non-empty .stl file, up to 25 MiB.

Choose a known 20-unit control

Download first; downloading does not submit your model. STL declares no physical unit, so interpret these coordinates as millimetres only when you choose that assumption.

Control	Actual report meaning
Closed cube	12 triangles, zero listed edge or face issues. Baseline only, not print approval.
Missing-face cube	10 triangles and four boundary edges; the known square face is absent.
Duplicate-face cube	13 triangles, one exact duplicate and three over-shared edges.
Malformed file	Parsing fails. It must not be read as a clean zero-finding report.

Try an example

Question to explore

How do a missing face, duplicate face and malformed file differ in the report?

Settings: Download controls without uploading. Explicitly submit one at a time to the Quality Checker for a server report.

Example file

Downloads this public control, then opens it locally. Your own file can still be chosen above.

Read the explanation · Download and compare controls · Methods and processing

Want to inspect the model first?

Open in STL Viewer to rotate and inspect your STL locally before running a quality check.

Turn a finding into one next action

Report finding	Next action
Parse failure, failed or unavailable report	No healthy zero-finding result exists. Check file/format diagnosis and the stated failure before retrying.
Boundary edge	Use the boundary checker and interpret the exposed boundary before closing a surface. A designed passage can have closed material walls.
A visible wall with no enclosed thickness	Compare the open sheet and closed plate controls before changing slicer settings.
Over-shared edge	Read the topology correction workflow; do not guess the extra face.
Exact duplicate or degenerate face	Review the source and the standard cleanup report, then recheck its downloaded copy.
Winding conflict	Compare the known orientation controls before changing a component.
No listed blockers or an uncertain shape	Check the local preflight, source CAD and the selected slicer preview. Inspect hidden internal faces when the outside looks right but interior layers do not.

The server compares exact stored coordinates and excludes degenerate triangles from edge counts. Its report components join through shared vertices; local STL Repair part selection uses shared edges. A clean report means only that supported checks found no listed blockers. Volume is unavailable for open or inconsistent reports; even a reported closed-mesh value cannot establish that untested spatial crossings or cavity intent are correct. If two closed surfaces overlap despite a clean edge count, compare them with the crossing-surface guide before changing the source model.