Exact diagnosis
Select an issue and Meshworthy takes you to the affected geometry.
Explainable STL repair
Repair STL files on Mac and see exactly what changed.
Find holes, non-manifold edges, flipped normals, self-intersections, and disconnected shells. Preview every proposed change before exporting a verified mesh.
Last reviewed
Expected outcomeA repaired model you can inspect, compare, and trust.
Why a repaired STL can still be wrong.
An STL file is a list of triangles. It has no notion of a solid, a unit, or design intent, so every defect is a statement about how those triangles connect. An edge used by only one triangle is an open boundary. An edge shared by three or more is non-manifold. A triangle that points inward reverses what the slicer treats as the outside.
Automatic repair tools usually close every gap they find. That includes the gaps you wanted, such as a socket, a vent, or the mouth of a hollow cup, and it can soften a sharp edge or merge two parts that were meant to stay separate. A green repaired badge says the mesh is closed. It does not say the model is still your model.
Meshworthy treats repair as a reviewed change. You see the defect, mark what must not change, preview what the repair touches, and the exported file is reopened and checked, because the file on disk is what your slicer reads.
Checks included in this workflow.
Meshworthy shows the affected geometry, applies the selected constraints, and checks the exported result. Limitations remain visible when a result requires manual review.
Repair comparison
Compare before and after with changed regions and measured surface deviation.
Intent Guard
Protect real openings, sockets, text, and thin details before repair.
Verified export
The exported file is re-opened and checked before Meshworthy calls it complete.
From diagnosis to a verified file.
01Diagnose
→Open the untouched STL. Meshworthy lists boundary edges, non-manifold edges and vertices, flipped faces, self-intersections, degenerate triangles, disconnected shells, and scale risks. Selecting a finding shows its exact triangles.
02Protect intent
→Mark openings, text, sockets, and thin details that are meant to be there, so the repair leaves them alone.
03Preview
→Review the changed regions and the measured surface deviation before anything is applied.
04Verify
The exported STL is reopened, and its topology, dimensions, and shell count are compared with what the preview promised.
What is free and what needs Pro.
Diagnosing a model and inspecting every defect in 3D is free in the Mac app. Repair is part of the one-time Meshworthy Pro unlock, with no subscription.
To look at an STL without installing anything, the free STL Error Checker runs in your browser. It is read-only, covers STL only, and never uploads the file.
What this does not do.
- Meshworthy does not generate supports, print settings, toolpaths, or G-code. Your slicer still decides how the model prints.
- Some defects need a design decision. When an intersection or an open surface has more than one valid fix, Meshworthy shows the affected geometry and the consequences instead of guessing your intent.
- A closed, correctly oriented mesh does not guarantee a good print. Wall thickness, supports, and material behavior are beyond what a mesh check can prove.
- Meshworthy is a preparation tool, not a sculpting or CAD application.
How to repair an STL file safely.
Use the seven-step checklist to diagnose topology, protect design intent, compare the change, and verify the exported file.
More guides on this topic
About explainable stl repair.
Can Meshworthy repair an STL automatically?+
Yes. It proposes a repair, shows what changed, and rechecks the result. Difficult openings can be handled with focused manual tools.
Does repair always mean watertight?+
Watertightness is one requirement, but it does not confirm that the design remains correct. Meshworthy also checks whether intentional openings or fine features were altered.
Does it upload my model?+
No. Analysis and geometry processing run locally on your Mac.
Which defects does it look for?+
Open boundary edges, non-manifold edges and vertices, inconsistent or flipped face orientation, self-intersections, degenerate and duplicate triangles, disconnected shells, and scale and thin-feature risks.
What if a repair would change a dimension?+
Meshworthy reports the measured surface deviation of each changed region before you apply the repair, so a change that matters to a fit or a thread is visible before export.
How is the Mac app different from the free STL Error Checker?+
The browser tool is read-only and covers STL files. The Mac app also opens OBJ, 3MF, and PLY, lets you inspect each finding in 3D with measurement, and, with Pro, repairs the model and verifies the export.
Know before you print.
On the Mac App Store. Diagnosis is free; Pro unlocks repair and preparation for $19.99, once — never a subscription. Model processing stays local.
Get Meshworthy for Mac ↗