Meshworthy
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Free browser tool

Check an STL for mesh errors, privately in your browser.

Find boundary edges, non-manifold edges, orientation problems, degenerate and duplicate faces, and separate shells in one local report. Everything runs on your device and your file is never uploaded.

Processing on your device Evidence, not a score No account required
Meshworthy STL Error Checker Private session · No upload

Drop one file here

Accepted: .stl up to 100 MiB. Binary and ASCII are both read. Nothing leaves your device.

Runs locally in your browser. Your model is not uploaded, stored, or included in analytics. Package metadata is shown only on this device. Review it before sharing screenshots or copied reports.

How it works

From file to evidence in three private steps.

  1. 01
    Read safely

    Your browser proves the binary or ASCII structure before it reads a single triangle.

  2. 02
    Map the topology

    Vertices are welded for analysis, then edges, shells, and orientation are computed on your device.

  3. 03
    Review evidence

    Named checks, an interactive overlay, and a copyable report. Nothing is uploaded, stored, or logged.

Blocking

What can stop a print.

  • Surface integrityOpen boundary edges, non-manifold edges, and watertight status from welded topology.
  • OrientationShared edge agreement and the inward or outward direction of every closed shell.
  • Separate shellsConnected components over shared edges, so a stray disconnected body is visible.

Boundaries

What the result does not claim.

  • Topology, not printabilityA clean mesh is not a proof of wall thickness, supports, or printer fit.
  • Review stays reviewSelf-intersection and contact are flagged for a person, never as a confirmed failure.
  • No silent repairThe tool reports evidence and never rewrites your geometry or hides a change.

Benchmark method

Known geometry with a known result. See the checker prove itself.

Every benchmark is primitive geometry authored inside this project, so its expected result is known by construction and its counts are committed alongside it. Binary and ASCII versions of the same shape return identical counts, and shuffling the triangle order never changes a count or a shell ID. Open a benchmark to watch an intentional opening report as a boundary rather than a hole the tool offers to fill.

Questions

Useful context before you check a file.

What does the STL Error Checker actually check?

It reads the mesh topology and separates print-blocking problems from advisory ones, the same way the Meshworthy Mac app does. The blocking checks are open boundary edges, non-manifold edges, orientation problems, and inward-facing closed shells. The advisory checks, which rarely stop a print on their own, are degenerate triangles, duplicate faces, self-intersection candidates, contact risks, and isolated debris candidates.

Is my STL uploaded anywhere?

No. The file is read, parsed, and analyzed entirely in your browser. No geometry, filename, or coordinate is sent over the network, stored, or included in analytics. You can watch the network panel and see that no request body carries your model.

Does it repair or change my file?

No. This tool is read only. It reports what it finds and never rewrites your geometry or offers a silently fixed download. Vertex welding is used only as an analysis index and never alters the preview or produces a repaired model.

Why does it say file units instead of millimeters?

STL stores no unit information, so a coordinate value is just a number. Labeling it as millimeters would be a guess. The report states the bounding box, diagonal, and weld tolerance in file units so you always know exactly what was measured.

What is a benchmark file?

Each benchmark is small geometry authored inside this project with a documented expected result. Open one without any file of your own to see how a known defect such as an open boundary or a non-manifold edge is reported.

Does a passing result mean the model is printable?

No. A clean topology result means no boundary, non-manifold, orientation, degenerate, or duplicate errors were found. It is not a proof of wall thickness, supports, printer fit, material behavior, slicing, or physical strength.

Ready to fix what you found?

Diagnose here. Repair with intent in Meshworthy.

Need to resolve these errors while protecting your design? Repair STL mesh errors on your Mac with Meshworthy. You can also follow the STL repair checklist for a safe workflow.