Free Online STL File Repair & Viewer
Check an STL and fix holes, flipped faces and broken triangles before you print — free, right in your browser, without uploading the file.
STL, OBJ or 3MF — processed in your browser, never uploaded
How to use it
- 1Choose an STL, OBJ or 3MF file, or drag it onto the box.
- 2Review the check: holes, open edges, flipped faces and broken triangles.
- 3Press “Repair file” and compare the original with the repaired model in the preview.
- 4Download the repaired file as STL or 3MF and open it in your slicer.
Common reasons STL files break
Files exported from artistic modelling tools such as Blender, AI-generated models and 3D scans often contain holes and flipped faces. Engineering CAD exports are usually clean.
After repair, check the model fits your printer and work out what it costs to print.
Open and view STL files online
Drop an STL, OBJ or 3MF to see it in 3D, spin it around and read its exact size, volume, surface area and triangle count — no software to install and nothing uploaded. It is a quick way to check a download from MakerWorld, Printables or Thingiverse before you slice it.
What “non-manifold” and “flipped normals” mean
A printable model must be a closed, watertight solid. The check flags the problems that stop slicers:
- Holes and open edges — gaps in the surface, so the model has no clear inside.
- Non-manifold edges — one edge shared by three or more faces, common after badly merged parts.
- Inconsistent or inside-out faces — normals pointing the wrong way, which confuse infill and walls.
- Degenerate and duplicate triangles — zero-area or doubled faces left behind by exporters.
STL repair in your slicer vs. online
Bambu Studio and OrcaSlicer can repair many files on import, but a separate check tells you what was wrong and gives you a clean file to share or sell. Scanned and AI-generated models benefit most.
Frequently asked questions
Why does my slicer reject an STL?
Usually because the model is not a closed solid: it has holes, open edges or faces pointing inward. Slicers need a closed solid to know what is inside and outside.
What does this tool fix?
It merges duplicate vertices, removes broken and duplicate triangles, makes face directions consistent, flips inside-out shells and fills holes. The result is then checked with Manifold, the same geometry library used by professional CAD tools.
Is my file uploaded?
No. All processing happens inside your browser and the file never leaves your device.
What if problems remain after repair?
Things like completely missing parts or self-intersecting surfaces need manual work. Try “Fix model” in Bambu Studio or OrcaSlicer, or correct the design in your CAD software.
Is this STL repair tool really free?
Yes — no sign-up, no file-size paywall and no watermark. The repair runs on your own computer.
Can I edit an STL here?
This tool views, checks and repairs. To change the shape, use Tinkercad, Fusion or Blender — see our tools directory.
More free tools
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Take the printer quiz or message us on WhatsApp and our team in Amman will help.