Free STL File Repair
Upload your STL to detect 3D mesh errors and download a fixed file instantly — processed entirely in your browser.
Drop your STL file here or click to browse
Binary & ASCII STL supported — up to 100 MB
How It Works
Upload your STL
Drag & drop or click to select your STL file. Both binary and ASCII formats are supported up to 100 MB.
Instant mesh analysis
The tool checks all 8 error categories in your browser — no server upload, no wait, no privacy risk.
Download repaired file
Get a fixed binary STL with degenerate & duplicate faces removed and normals recomputed from geometry.
What Does the Analyzer Check?
The same criteria used by professional tools like Meshmixer and Netfabb
Naked edges
Edges shared by only one triangle — open holes in the surface. Each boundary loop is traced and filled with a centroid fan patch to close the mesh.
Planar holes
Flat boundary loops filled automatically with a centroid fan. Common in exported CAD models where internal faces were removed.
Non-planar holes
Curved holes get an approximate centroid fill that closes the mesh. Complex organic shapes may benefit from a manual clean-up pass for perfect quality.
Non-manifold edges
Edges shared by 3 or more faces — extra conflicting faces are removed to restore valid 2-manifold topology that every slicer expects.
Inverted normals
Faces whose surface normal points inward instead of outward. Causes ghost walls, slicing artifacts, and incorrect volume calculations.
Duplicate faces
Two or more triangles occupying the exact same position. Inflates file size and confuses slicer boolean operations.
Degenerate faces
Zero-area or near-zero-area triangles (collinear vertices, collapsed edges). These contribute no geometry but waste memory.
Disjoint shells
Separate disconnected mesh components inside one file. May print fine but can confuse slicers expecting a single solid body.
✓ = automatically fixed in the output file · ⚠ = detected & reported — requires manual repair
Frequently Asked Questions
What does this STL repair tool actually fix?+
The tool automatically removes degenerate faces (zero-area triangles), duplicate faces (identical overlapping triangles), and corrects inverted normals by recomputing them from the mesh geometry. Naked edges, non-manifold edges, and non-planar holes are detected and reported but require manual geometric reconstruction that is beyond browser-based processing.
Is my file uploaded to a server?+
No. All processing happens entirely in your browser using JavaScript. Your STL file never leaves your device. This makes the tool safe for confidential product designs and prototype files.
Why does my slicer say the STL is broken?+
Slicer software like Cura or PrusaSlicer requires a "watertight" mesh — a closed surface with no holes or overlapping geometry. Naked edges (open holes), non-manifold edges, and inverted normals are the most common causes of slicing errors. Use this tool to identify exactly which issues your file has.
What causes naked edges in an STL file?+
Naked edges usually occur when faces are deleted leaving an open boundary, when a Boolean operation fails to merge surfaces cleanly, or when a surface model is exported to STL without being converted to a closed solid first. CAD tools like SolidWorks and Fusion 360 sometimes produce them when complex fillets or shells are exported.
Can this tool fix non-manifold edges?+
No — non-manifold edges (edges shared by 3 or more faces) require geometric reconstruction. The tool detects and counts them so you know the extent of the problem. For complex repair, our team can fix the file manually via WhatsApp.
What is the difference between planar and non-planar holes?+
A planar hole is a gap whose boundary loop lies entirely in a flat plane — these can be filled by cap-filling algorithms. A non-planar hole has a curved boundary (e.g. a hole in the side of a sphere) and requires more sophisticated algorithms to patch correctly without introducing distortion.
🔒 Your file is processed entirely in your browser — nothing is ever sent to our servers.