Online STL Repair
& Mesh Checker

Free, and there is no card. A free STL repair covers files up to 25 MB and 5 runs a day, which is more than most people need for a one-off broken file. There is no signup step in the way either: upload, read the report, download. Paid plans exist for larger files and higher volume, and nothing on this page is gated behind them.

STL file repair has two halves, and most tools only show you the second. Check mode inspects the mesh and hands back a defect report without touching the file, so you can see whether anything is actually wrong before you change it. Repair mode does the same inspection, applies the fixes, then re-measures so you can compare the result against the original. Running the check first costs you nothing and sometimes tells you the file was fine.

That is what this page is. STL repair online means the mesh work happens on our servers, so a Chromebook does the same job as a workstation and there is no download beyond the repaired file itself. The trade-off worth stating: your file is uploaded. If the geometry is confidential, desktop software keeps it on your machine, and that is a real reason to prefer it.

Slicers say "model is not manifold" and either refuse the file or silently auto-fix it. The report gives you numbers: how many open boundary edges, how many non-manifold edges, how many duplicate faces, the dimensions and enclosed volume. You see what is wrong before deciding to change anything, and after a repair you can compare volume and dimensions against the original.

Usually imperceptibly. Closing holes and removing duplicate faces does not move geometry, and the Cleanup level never does. The honest exception: welding hairline cracks (the opt-in Aggressive level) can shift a surface, and in our own worst-case test a badly cracked mesh lost volume that way. That is why the report always shows before/after dimensions and volume, and warns when they moved more than 1%. If a critical dimension matters, check it after repair.

Your mesh is essentially flat or encloses no volume: a plane, a relief, or a scan patch rather than a closed part. Repair can technically close it into a solid, but the result may not be what you want to print. Give it thickness in your modeling tool instead.

Mostly exports: boolean operations that leave internal faces, meshes merged without cleanup, low-tolerance exports that crack seams, and scaling that produces zero-area triangles. 3D scans add debris and holes. AI mesh generators frequently produce overlapping, non-manifold geometry.

In order: weld duplicate vertices, drop degenerate and duplicate faces, fix winding and normals, fill holes, handle disconnected shells (configurable), and, only if defects remain, rebuild the surface with pymeshfix. Three levels: Cleanup stops after the safe steps, Standard adds reconstruction, Aggressive may also snap-weld hairline cracks. Every step is printed to the job console as it runs.

No. Heavily self-intersecting or garbage geometry can survive repair, and open surfaces are a modeling problem, not a repair problem. When something cannot be fully fixed the report says so instead of pretending. The output is still usually closer to printable than the input.

Yes. Upload an OBJ and you get a repaired STL back (or a report in check mode). Color and texture data is not preserved; the output is print-oriented geometry.

Uploads are deleted within about an hour and results within 24 hours. Free accounts: 25 MB per file, 5 conversions a day, no signup needed.