Repair STL online
Your slicer says "not watertight" or "non-manifold"? The print check shows you for free what exactly is broken. The repair engine (PRO) fills holes, flips wrongly oriented faces and removes degenerate triangles — and you see Original, Repaired and Diff side by side before you export.
Nothing is uploaded: loading, print check and repair run entirely locally in your browser. Diagnosis is free, fixing is PRO.
What you can do here
- Free diagnosis: open edges, non-manifold edges, degenerate triangles
- Repair (PRO): fill holes, unify normals, remove degenerates
- Before/after comparison with diff colouring
- Print-ready export as STL or 3MF — volume change is reported
How it works
- Drag and drop a file into the viewer (or "Open file").
- Tap "Print check" — free, including wall thickness and material estimate.
- If there are problems: "Repair" (PRO), compare Original/Repaired/Diff, export as STL or 3MF.
Frequently asked questions
- Are my 3D models uploaded anywhere?
- No. Loading, viewing, diagnosis and repair run entirely in your browser or on your device — there is no server that ever receives the model file.
- Which file formats are supported?
- Viewing: STL, OBJ (with MTL and textures), GLB, glTF and ZIP archives containing gltf+bin/textures. Draco- and Meshopt-compressed GLB files are decoded automatically. USDZ is not displayed but generated: every model can be exported as a true-scale USDZ for AR Quick Look.
- What is the difference between Free and PRO?
- Free includes the complete viewer with every print diagnostic (open edges, watertightness, wall thickness, material estimate) and no limits. PRO unlocks the repair engine, the print-bed fit check, print-ready STL/3MF exports and watermark-free images. In short: diagnosis is free, fixing is paid.
- What does the repair engine fix — and what doesn't it (yet)?
- It fills holes, flips wrongly oriented normals and removes degenerate triangles — the most common reasons a slicer rejects an STL. Self-intersections and hollowing models are not included yet.
- Can I use this from CI or an AI agent?
- Yes. The same engine also runs as a command-line tool and as an MCP server for AI agents — offline, no upload, with machine-readable JSON and diagnostic codes instead of prose. Nothing to install: npx -y 3dviewer-cli check model.stl. In a pipeline the run ends with an error exit as soon as a model has defects. The print check is just as free there; repair and print-ready export need a PRO licence.
- Is there an app as well?
- Yes, a native iOS app with the same features is in preparation. A web purchase can also be unlocked in the app via a redemption link/QR code — no account needed.