STLRepair
STLRepair is a free browser-based STL checker and repair tool aimed at anyone preparing a 3D model for printing. Users drop a binary or ASCII STL file into the web app, which parses the triangles, builds mesh topology, and reports on five core issue families: open boundary edges, non-manifold edges, normal direction mismatches, duplicate faces and degenerate triangles. Analysis runs locally in the browser, and the site states that uploaded files are not sent to a production server for the public workflow. The tool positions itself as a conservative, low-risk repair step rather than an aggressive mesh healer. It applies what it describes as safe fixes — for example recalculating facet normals or clearing repeated surface triangles — while leaving riskier problems such as open boundary loops and shared-edge topology as report-only findings for manual repair elsewhere. Each run produces a mesh health score, a per-issue breakdown and a preview of the result so users can verify the exact output before downloading. Outputs include the repaired STL file and a JSON report, which the site frames as a verification step before final slicer validation. The public anonymous workflow has stated limits of roughly 10 MiB or 100,000 triangles per file, with an engine identifier reading 0.2.0-verified-local-export. Sample models on the site cover decorative, functional and mechanical shapes, and the tool links to a blog of repair guides.
- Category
- 3d Animation
- Pricing
- Unknown
Problem solved
Slicers frequently fail or produce bad prints when an STL contains mesh defects such as open boundaries, non-manifold edges, flipped normals, duplicate faces or degenerate triangles. STLRepair gives creators a quick, free, browser-based gate check that identifies these defect families, applies only conservative fixes, and lets them verify and download the corrected mesh plus a JSON report before committing to slicer validation.
Use cases
- Check an STL for mesh defects before slicing or 3D printing
- Apply conservative fixes such as normal recalculation and duplicate-face removal
- Verify repaired geometry against a mesh health score before downloading
- Generate a JSON diagnostic report of mesh issues for documentation or sharing
- Diagnose open boundary and non-manifold edge problems flagged as report-only
- Screen downloaded or third-party STL models for hidden topology errors
- Use as a lightweight pre-flight step in a hobbyist or small-shop 3D printing workflow
Audience
- Hobbyists
- Designers
- Content Creators
- Startups
Pros
- Free to use with no CAD installation required
- Analysis runs locally in the browser, so files are not uploaded for the public workflow
- Reports five distinct, well-defined mesh issue families with a health score
- Conservative repair stance avoids silently altering geometry with risky fixes
- Provides downloadable repaired STL plus a JSON report for verification
Cons
- Public workflow caps files at about 10 MiB or 100,000 triangles
- Some issues, such as open boundaries and non-manifold edges, are report-only and not auto-fixed
- Only supports STL input rather than other mesh or CAD formats
- Exact pricing, licensing and long-term roadmap details are not published clearly
Official website: https://stlrepair.app/
Canonical LambdaBase page: https://www.lambdabase.com/tools/stlrepair