Use this free STL fixer to inspect your 3D model, repair supported mesh issues, and download the checked file. STL repair runs in your browser; your model stays on your device.
ASCII or binary STL · Up to 50 MB (50,000,000 bytes)
JavaScript is required to check and repair your STL locally in the browser.
Choose a file to check whether this option applies.
Clicking Repair uses the visible option above. Only up to two triangular openings are supported: each edge ≤ 6% of the mesh diagonal, total patch area ≤ 0.2% of surface area. Larger or intentional openings need a mesh editor.
STL has no unit. Scaling changes coordinates only when you apply it. Every scaled file is checked again; repeated applications start from the unscaled result. Mesh simplification is a separate operation and is not included.
Choose & inspectSee the real 3D mesh and diagnosis.
Repair & compareReview Before, After and each change.
DownloadOptionally scale, recheck and save.
Choose an STL to inspect its actual 3D geometry and measurements.
STL repair checks how a model’s triangles connect before changing them. Use an STL fixer to identify broken surfaces and review the result, rather than assuming every opening is a defect.
These illustrations explain common STL repair problems. This STL fixer provides conservative cleanup and selected local repairs; it cannot validate wall thickness, infer design intent or rebuild severely damaged models.
An open boundary is an edge shared by only one triangle. Before mesh repair, distinguish a missing patch from an intended opening. A mesh checker cannot infer which surface you designed.
Repair approach: Mesh repair should add faces only where a gap needs closing.
In this tool: This tool selects small-hole closing by default for open boundaries. Uncheck it for intended openings. Only limited small triangular holes are supported; larger gaps need a mesh editor.
Triangle vertex order determines the outward side. Inconsistent winding can confuse a slicer about inside and outside; mesh repair can correct compatible face directions without changing dimensions.
Repair approach: The repair process aligns face winding and rechecks the shell.
In this tool: This tool supports orientation cleanup. STL repair does not recover missing CAD surfaces or correct wall thickness.
Coincident triangles can create redundant or conflicting surfaces. mesh repair removes exact duplicates while retaining the remaining geometry, even when the overlap was invisible in a normal viewer.
Repair approach: The repair process identifies repeated faces and checks the remaining connections.
In this tool: This tool supports exact duplicate cleanup. STL repair counts appear in Before/After results, and the exported file is checked again.
A collapsed triangle has no usable surface area. mesh repair removes these invalid faces, which may expose an opening elsewhere in the mesh.
Repair approach: The repair process removes degenerate triangles and rechecks topology.
In this tool: This tool reports removed faces. STL repair can improve the mesh without making it watertight; review any remaining open boundaries.
A closed surface normally has two faces at each edge. mesh repair becomes ambiguous when extra faces, internal sheets or incompatible shells meet.
Repair approach: Use a mesh checker to locate affected topology, then review the intended solid in your source CAD.
In this tool: This tool highlights non-manifold edges and vertices. General non-manifold reconstruction is outside its STL repair capability; unsupported results are refused.
Crossing mesh surfaces can obscure which region is inside the model. mesh repair may require separating or rebuilding the surfaces, not just removing triangles.
Repair approach: Inspect the crossing region before using a mesh checker to repair STL geometry.
In this tool: This tool handles selected small local cases only. Widespread self-intersections need another STL repair workflow. Some detected intersections have no colored location.
Learn more about STL geometry and repair methods in the Library of Congress STL format description, Blender's 3D Print Toolbox manual and CGAL's polygon mesh repair manual. Return to the STL fixer to check your STL.
What to expect before you repair STL files and take them back to your workflow.
An STL file describes a 3D surface using triangles, without reliable units or material data. An STL fixer checks this mesh rather than the original CAD design. Before STL repair, confirm your model’s unit convention; afterward, check dimensions in your slicer.
This STL fixer is free to use, with no account or subscription required. STL repair accepts ASCII and binary files up to 50 MB (50,000,000 bytes). Basic processing allows 1,000,000 triangles; local intersection processing allows 100,000. Coordinates must be finite and within the supported range.
STL repair supports exact duplicate and degenerate-face cleanup, compatible orientation correction, controlled small triangular hole closing, and selected local intersections. This STL fixer selects small-hole closing for open boundaries; uncheck it for intended openings. Large holes, general non-manifold reconstruction and widespread intersections are refused.
STL repair aims to preserve dimensions. Cleanup removes invalid faces; orientation correction changes winding; hole closing adds triangles. This STL fixer does not automatically scale your model or infer units. Inspect Before/After geometry. Optional uniform scaling creates a separately checked export.
Your STL file is read locally. This STL fixer does not send file names, contents or mesh data to a server. STL repair loads its program resources into your browser; the page has no file-upload endpoint.
Choose a file in the STL fixer to inspect its geometry, measurements and diagnosis. Review the small-hole option, then select Repair STL. Compare Before and After and read the reported changes. Download the checked STL repair result, or apply optional uniform scaling first. Inspect dimensions and layers in your slicer.
STL repair stops after 60 seconds or when a check fails. This STL fixer explains the issue and withholds an unverified download. Choose a file again to restart. Dense coplanar meshes may time out even below the size limit; try source-CAD correction or a mesh editor.
No. An STL fixer checks geometry, not wall thickness, strength, printer tolerances, supports or materials. A successful STL repair does not guarantee every slicer interprets the model identically. Review the downloaded file’s dimensions and layer preview before printing.