Want to inspect the model first?
Open in STL Viewer to rotate and inspect your STL locally before running a quality check.
Free mesh preflight
STL Quality Checker
Check an STL file for common mesh problems before 3D printing, including open edges, non-manifold geometry, duplicate triangles and orientation issues.
Choose your file
Select a .stl file.
Select a non-empty .stl file, up to 25 MiB.
Catch common STL issues before printing
A mesh quality check can flag topology and orientation problems early, helping you avoid failed slicing or unexpected gaps in a print. Submit your STL above to start a job. The report appears automatically when the analysis finishes.
How it works
Upload an STL and InspectMesh checks its triangles, edges and surface orientation for common mesh problems.
What the results mean
Open edges and non-manifold edges can prevent a clean solid. Duplicate or degenerate triangles add invalid geometry, while orientation issues can affect inside and outside calculations. Ready for slicing means these checks found no listed mesh blockers, not that every printer setting is correct.
FAQ
What is an open edge?
It is an edge used by only one triangle, often indicating a hole.
What is a degenerate triangle?
It has no usable area because its vertices collapse together or lie on a line.
Should I repair duplicate triangles?
Usually yes, because overlapping faces can confuse downstream tools.
STL Manifold Checker · STL Watertight Checker · STL Print Preflight Checker · STL Repair Tool · How to Fix Non-Manifold STL Files · How to Repair an STL File · How to Make an STL File Printable · All STL tools
Use defect fixtures to interpret a quality report
Understand why edge counts do not rule out intersections
Deleting a square face from a 20 mm cube creates four boundary edges. Adding one duplicate face creates three edges shared by more than two triangles. A repeated-vertex triangle is degenerate. Two separate closed cubes have two shells; their design intent still needs review.
Interpret the result and choose the next step
These owned software fixtures are available through the batch workflow and its report. Geometry counts are findings, not a physical printability guarantee. Choose the correction from the actual defect and verify the new export against the original dimensions and shape.
Open a mixed collection exampleDownload the owned 20 mm cube sample, or the declared-inch 3MF sample. For a G-code preview, use the actual Arachne slicer export. Model samples are illustrative geometry; the G-code is for inspection and must not be sent to a printer.
Numerical scenarios are illustrative software examples, not physical print tests.