Guides
Start here
Every guide below starts from a symptom you have actually seen — a slicer that refuses the file, a print that comes out hollow — and ends with a fix you can run in your browser. Each one also says plainly what repair cannot do, because a tool that overclaims costs you an evening.
Start with the symptom
- STL won't slice? The 6 usual causes, and how to fix each — the triage page. Work out whether you have a mesh problem or a settings problem before you fix the wrong one.
Mesh defects
- How to fix a non-manifold STL — what the word means, why your slicer rejects it, and the three defects behind it.
- How to fix holes and open edges in an STL — the most common single fault, and usually invisible: one missing triangle, not a crater.
- How to fix flipped and inverted normals — the mesh is closed, renders perfectly, and still prints inside-out.
Models from AI generators
- Why your AI-generated model won't print — the generator was optimising an image, not an object. Watertightness was never in the loss function.
- How to make a Tripo model printable — without Blender, and without touching the shape you asked for.
- How to fix a Meshy model for 3D printing — internal faces, floating fragments, and why STL throws your texture away.
Choosing a tool
- Meshmixer is no longer maintained — what to use instead — legacy, not deleted. An honest comparison, including where our own tool loses.
- The best free STL repair tools in 2026 — written by the people behind one of them, which is exactly why it names the two that repair more than we do.
Already know what's wrong?
Drop the file into SliceReady. It repairs in your browser, nothing is uploaded, and the report tells you the truth about what was fixed and what was not.