The 3D provider Tripo has released FixSTL, a free tool that checks and repairs STL files directly in the browser. You need no account and no installation, and the finished file gets no watermark. According to Tripo's description, a Web Worker processes the file locally, and neither the model nor the file name is transferred to a server.
FixSTL first shows mesh errors in an inspection report and only repairs them afterwards, once you press the button. Whether an attempt is worthwhile before printing depends on what the repair achieves and where the repair stops.
What does FixSTL check and repair?
The inspection report lists open edges, non-manifold geometry, flipped faces, self-intersections, duplicate and zero-area triangles, as well as loose shells. The tool only estimates wall thickness. As an example, Tripo shows a model of Milan Cathedral with 3,806 triangles: The report counts 56 open edges, 294 non-manifold edges, 26 flipped faces, 20 zero-area triangles, and 6,452 self-intersections there.
The repair closes holes, removes duplicate and zero-area triangles, joins loose vertices, and orients the faces consistently. Thanks to the inspection report, you don't repair blindly.
Where are the limits of the repair?
FixSTL intervenes only slightly in the model. FixSTL fills holes only up to about one third of the model size; larger openings and parts that touch only at an edge or corner remain unchanged. The report only flags overlapping parts and Boolean remnants; for those you need a Boolean union in a modeling program. Interior walls are preserved, and FixSTL flags walls that are too thin without increasing the wall thickness.
Was FixSTL repariert und was nicht
Reichweite der Reparatur nach den Angaben von Tripo, Stand 9. November 2026
- Löcher bis etwa ein Drittel der Modellgröße werden geschlossen
- Doppelte und flächenlose Dreiecke verschwinden
- Umgekehrte Flächen richtet FixSTL einheitlich aus
- Überlappende Teile und boolesche Reste bleiben liegen
- Innenwände und Kantenkontakte bleiben unverändert
- Zu dünne Wände werden nur markiert, nicht verdickt
Ein bestandener Check garantiert keine Druckbarkeit
Quellen: Tripo, 3DRUCK
In addition, the surface may shift only within limits: by at most 0.1 percent of the diagonal of the bounding box for most interventions, and by at most 1 percent for rebuilt surfaces. If an intervention goes beyond that, FixSTL discards the change. The tool fixes self-intersections only in areas under 15 percent of the model. FixSTL never changes scale or units; for functional parts, you should still check critical dimensions yourself.
Tripo compares FixSTL with Blender and MeshFix: Of 131 damaged test files, FixSTL repairs 57 completely, Blender 41, and MeshFix 40. Of 69 intact files, FixSTL changes none. This series of measurements comes from Tripo itself.
Which files and browsers work?
FixSTL reads only STL files, ASCII and binary; the site does not mention 3MF and OBJ. Per file, a maximum of 100 MB and 2,097,150 triangles apply, and up to 20 files totaling 200 MB can be processed at the same time. Checking a 100 MB mesh takes seconds, repairing it several minutes, with a progress indicator and a cancel button. What you usually download is a binary STL file; multiple files come as a ZIP with a CSV overview.
The full check is handled by a Rust engine via WebAssembly. If the browser cannot do that, a simpler version steps in that does not detect self-intersections. The report shows which version ran.
What this means for you
Load a file that your slicer complains about into FixSTL and read the inspection report first. Then repair, and load the new file into the slicer again. Tripo itself warns that a passed check does not guarantee printability: wall thickness, overhangs, scale, and supports remain your responsibility.
If a file is one of the cases FixSTL does not repair, such as overlapping parts, you turn to a modeling program; Tripo names Blender and Meshmixer for this. For heavily damaged meshes, Tripo advises having the model regenerated, meaning its own tools. A note in our own interest.
According to Tripo's description, customer models and your own designs stay on your computer. The anonymous usage statistics send only totals such as the number of triangles and errors.
3DRUCK published the article on FixSTL on November 9, 2026.
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