Browser-local repair
STL repair
Fix common STL mesh defects without uploading the file. Safe repair welds vertices that land in the same tolerance-sized grid cell, drops zero-area triangles and makes triangle winding consistent, and it shows you a measured before-and-after table before anything is exported. What it will not do is invent geometry: a hole stays a hole, and you are told exactly how many open edges remain.
Drop your STL files here
STL, OBJ, PLY, GLB, glTF, 3MF, SVG and DXF. Nothing is uploaded: files are read and repaired inside this tab. Checking what this device can handle...
Queue
No files yet. Drop models above, or use the file picker.
Inspection
Add a model to see its dimensions, mesh health and estimated volume.
Output
Units
Size and placement
Repair and cleanup
These can change the shape, so they need a before-and-after review before export.
These changes can alter the geometry
Welding, dropping triangles, merging meshes and repair all rewrite the mesh. Review the before and after figures, then confirm, and export will unlock.
1 operation will run, in this order
- Safe repair: weld duplicates, drop zero-area triangles, fix winding
Review the geometry changes above before converting.
What this STL repair does and does not do
- Holes are never filled. Closing a gap means deciding where surface should be, which is a modelling decision about your design, not a file correction. The inspection panel counts open edges before and after so you know precisely what is still open.
- No remeshing, decimation or simplification happens, and self-intersections are not resolved. Safe repair welds vertices by grid cell, removes degenerate triangles and corrects winding; it does not rebuild your mesh into something smoother or smaller.
- Winding is made consistent across each connected shell, and a closed shell is then oriented outward using its enclosed volume. For a shell that is not closed the sign of the volume proves nothing, so it is left consistently wound rather than flipped on a guess.
- Welding snaps vertices to a grid at a tolerance that is shown with every result. Two points a hair under the tolerance apart but either side of a cell boundary stay separate, which is the honest cost of a deterministic weld.
- An STL declares no unit, so nothing here guesses one. Welding runs in the model's authored units, and the suggested tolerance is derived from its bounding box rather than assumed in millimetres.
- Separate shells are left separate unless you explicitly merge them, because merging changes object identity. The inspection panel counts them so you can see what you have.
Troubleshooting
My slicer still reports non-manifold edges after repair
Non-manifold is a broader claim than duplicates or degenerates: an edge shared by three or more triangles, such as two solids fused along a face, is also non-manifold and is real geometry that repair will not delete for you. Check the count in the inspection panel; if it did not drop, the cause is structural rather than dirty data.
The mesh has holes and repair left them open
That is the contract, not a failure. Look at the before-and-after table: if the open-edge count is unchanged, no surface was invented. To close holes you need mesh software that models the missing patch, with you choosing how it is shaped.
The model shows as inside out
Run safe repair on a closed shell and the winding is made consistent and oriented outward using the enclosed volume, which fixes inverted faces. If the shell is open, close it first in your modelling tool; outwardness is not decidable from an open surface alone.
The preview says nothing would actually change
Then the selected operations found nothing to change: no vertices shared a weld grid cell, no zero-area triangles were found, and the winding was already consistent. Export it as-is; there is nothing to approve and the review gate will unlock immediately once you have read the figures.
Questions
Why will it not fill the holes?
Because filling a hole invents surface. Where a cap goes and how it is shaped are decisions about your design, and a tool that makes them silently produces files that look plausible and are wrong. This repair removes genuine defects — duplicates, degenerates, inconsistent winding — and reports everything else as measured counts.
What exactly does safe repair change?
Three things: vertices that round into the same tolerance-sized grid cell are welded to the first representative point, zero-area triangles are dropped, and triangle winding is made consistent across each connected shell — with closed shells oriented outward by their enclosed volume. The before-and-after table quantifies the resulting mesh before you approve.
Is my STL uploaded anywhere?
No. There is no upload endpoint in this project, no server-side file processing and no file storage. The model is read and repaired locally in a dedicated browser worker, and the site Content Security Policy blocks cross-origin file transfer.
Will repairing make my file print correctly?
It can correct weldable duplicates, zero-area triangles and inconsistent winding, but it cannot guarantee a printable model. Holes, self-intersections and structural non-manifold geometry remain. The inspection panel tells you what changed and what remains before you export; your slicer is the final check.
Does repair change the size or dimensions?
It can make a bounded change: vertices in one weld grid cell use the first vertex as their representative, so a coordinate can move by up to the displayed tolerance on each axis. Dropping a degenerate triangle can also remove an unused extreme point. The before-and-after dimensions and volume are shown before approval; scaling, unit assignment and orientation remain separate controls.