Free STL Repair Tool
Our free STL repair tool fixes broken 3D models online in seconds: it fills holes, repairs non-manifold edges and flipped normals, and gives you a watertight STL that slices without errors.
Drag & drop your STL here
or click to browse · STL, OBJ or 3MF · up to 50 MB
Free: 5 repairs per day · files up to 50 MB · repaired files deleted after 24 hours
What does the STL fixer repair?
Slicers need a closed, watertight mesh to know what is inside your part. These are the STL errors the tool finds and repairs automatically — the same problems behind “non-manifold” and “open mesh” warnings in Bambu Studio, PrusaSlicer and Cura.
Holes and open edges
Gaps where triangles don't meet — the most common reason a slicer says a model is not watertight or not manifold. The STL fixer closes them with new faces.
Non-manifold edges
Edges shared by three or more faces, or stray faces sticking out of the surface. These confuse slicers about what is inside and outside the model.
Flipped (inverted) normals
Faces pointing inward make parts of a model look inside-out, which can produce missing walls or empty layers. Normals are made consistent again.
Duplicate and degenerate faces
Overlapping copies of the same triangle and zero-area "sliver" triangles, typical after merging meshes or exporting from CAD. They are removed.
Loose, unconnected faces
Floating triangles that aren't attached to anything. They add errors without adding geometry, so the STL repair removes them.
OBJ and 3MF to STL
Upload an OBJ or 3MF and you get a clean binary STL back — handy when your printer or slicer only takes STL.
What it can't fix automatically: self-intersecting parts, walls thinner than your nozzle, and models exported at the wrong scale. The repair report lists anything that is left, so you know exactly what to fix in your 3D editor.
How to repair an STL file online
- 1
Upload your model
Drop an STL, OBJ or 3MF (up to 50 MB) into the tool above. No account needed.
- 2
Review the repair report
See every problem found and fixed — holes, non-manifold edges, flipped normals — with a before/after check.
- 3
Download or print it
Download the repaired STL, or send it straight to our 3D printing service for an instant quote.
Why do STL files break?
An STL is just a list of triangles, with no information about which ones belong together. Small mistakes during modeling or export leave gaps and overlaps that a slicer can't interpret:
- Separate meshes that were never joined — common in Blender and SketchUp exports.
- Boolean operations (union, difference) that leave slivers and duplicate faces behind.
- Sculpted and scanned models with tiny holes and inside-out patches.
- Old or heavily remixed downloads from model libraries, exported by tools that didn't check the mesh.
- CAD exports at low resolution, which create zero-area triangles along curved edges.
Repairing the STL before slicing avoids missing walls, stray strings of plastic and failed prints — and it is faster than re-exporting when you don't have the original project file.
Repair the STL or let the slicer fix it?
Many slicers try to patch small errors while slicing, but they guess differently and don't tell you what changed. Repairing the STL first gives you one fixed file that behaves the same in every slicer, a report of what was repaired, and a model you can share, sell or send to a print service with confidence.
Your file stays private: the upload is deleted as soon as the repair finishes, and the repaired STL is deleted after 24 hours.
STL repair FAQ
Is this STL repair tool really free?
Yes. You can repair up to 5 files per day for free, with no sign-up and no watermark. The email field on the download is optional.
What does the STL fixer repair?
It fills holes, fixes non-manifold edges, makes flipped normals consistent, and removes duplicate, degenerate and loose faces. The result is a watertight STL that slicers like Bambu Studio, PrusaSlicer, Cura and OrcaSlicer can slice.
Will repairing my STL change its size or shape?
No. The model is not scaled, moved or smoothed. New triangles are only added to close holes, and faces are only removed when they are duplicates, zero-area slivers or not connected to the model.
Which files can I upload, and how large?
STL (binary or ASCII), OBJ and 3MF files up to 50 MB. OBJ and 3MF files are converted to a single STL, so colors and multiple plates are not kept.
Can it fix self-intersecting or very broken models?
Not automatically. Self-intersections, walls that are too thin and heavily damaged scans need manual repair in a 3D editor such as Blender or Meshmixer. The report tells you which problems are left.
What happens to my file?
Your upload is processed on our server and deleted right after the repair. The repaired STL is kept for 24 hours so you can download it, then deleted. We never share or sell your models.
Can you 3D print the repaired model for me?
Yes. Click “Get an instant print quote” after the repair and the repaired model opens in our 3D printing service, where you pick the material and color and see the price right away.
Need it printed?
Upload your model for an instant 3D printing quote — PLA, PETG and TPU, printed on a Bambu Lab H2C in Los Angeles and shipped to you.
Get a 3D printing quote →Selling 3D models?
Sell your designs as physical products: we print, pack and ship every order, and you earn on every sale. Your files are never sold.
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