Free Online STL Repair Tool
Analyze your STL for mesh issues and fix them instantly in the browser. Detects duplicate vertices, degenerate faces, bad normals, and more.
What Gets Detected & Fixed
The tool scans for common STL issues and applies the ones that can be safely automated.
Duplicate vertices
Auto-fixedMultiple vertices at the same position inflate file size and can confuse slicers. Merging them reduces geometry and improves manifoldness.
Degenerate faces
Auto-fixedZero-area triangles (where two vertices share the same position) are invisible but break slicers and CAD tools. They are removed automatically.
Bad / missing normals
Auto-fixedIncorrect normals cause rendering artifacts and shading issues. Recomputing from geometry produces consistent face directions.
Inverted normals
Manual optionIf the model appears inside-out in your slicer, all face windings may be flipped. The tool provides a one-click option to reverse all normals.
Non-manifold edges
DetectedEdges shared by more than two faces cannot be printed. These require manual topology repair in Meshmixer, Blender, or similar tools.
Open boundaries / holes
DetectedA non-watertight mesh will fail most 3D printer slicers. Hole filling requires mesh surgery — the tool flags the boundary edge count for manual follow-up.
How It Works
Upload your STL
Drop or browse an STL file — binary or ASCII format both work.
Review issues
The tool scans your mesh and lists every issue found with severity and fix availability.
Download repaired file
Select the fixes to apply and download the cleaned STL in seconds.
Why Use This Tool
Fully private
All processing happens in your browser with WebGL. No files are ever sent to a server.
Instant analysis
Mesh analysis and repair runs in seconds, even for large files with hundreds of thousands of faces.
No software needed
Works in any modern browser — no Blender, Meshmixer, or CAD software required for basic repairs.
Frequently Asked Questions
What issues can this STL repair tool fix?
The tool can automatically fix duplicate vertices, degenerate (zero-area) faces, and bad or missing normals. It also detects non-manifold edges and open boundaries, and reports how to address them manually.
Does the file get uploaded to a server?
No. All analysis and repair runs locally in your browser using WebGL and JavaScript. Your STL files never leave your device.
Why does my STL fail to 3D print?
Common causes include non-manifold edges, open mesh holes, inverted normals, and duplicate or degenerate geometry. This tool identifies and fixes these issues where possible.
Can this tool fix non-manifold edges and holes?
The tool detects non-manifold edges and open boundaries but cannot automatically close holes or rebuild non-manifold topology — these require manual repair in tools like Meshmixer, Blender, or Netfabb.
Is there a file size limit?
There is no hard limit. Files up to several hundred MB work fine in most modern browsers. Extremely large files may be slow depending on your device memory.