How to use the STL Viewer
- Choose or drop an STL file.
- Rotate with drag, zoom with the wheel or pinch, and pan with right drag or two fingers.
- Review the model bounds and complexity.
- Choose the intended STL unit, activate Measure distance, then select two visible mesh points.
- Use Inspect cross-section to move a cut through the displayed mesh and look for internal geometry that is hard to see from the outside.
What the Viewer shows
The viewer calculates the model's bounding dimensions and triangle count directly from its geometry. STL coordinates have no native unit, so confirm scale in your slicer.
Bounding dimensions describe the full model. Point-to-point measurement checks two selected features, such as an opening width or mounting-tab length. Read how to measure a 3D model for a practical workflow.
Inspect a cross-section
Choose Inspect cross-section below the viewer, choose an X, Y or Z cut axis, then move the cut position through the displayed model. It hides one side of the mesh so you can inspect internal geometry from different angles. Read how to inspect STL and 3MF cross-sections for a careful workflow and its limits.
Locate mesh issues
Open edges can mean gaps in a surface, while non-manifold edges can confuse slicers. Highlighting is diagnostic: it shows reported locations but does not repair the model. Use the STL Quality Checker, STL Watertight Checker, STL Manifold Checker, or guide to fixing non-manifold STL files for the next step.
FAQ
Does my STL file get uploaded?
Viewing is local. If you explicitly request Locate mesh issues, the file is uploaded for server analysis through the Quality Checker.
Can I view ASCII and binary STL files?
Yes, both common STL encodings are supported.
Why do STL dimensions not specify mm or inches?
STL stores coordinates but not a unit system.
How accurate is the measurement tool?
It measures points on the displayed mesh. Results depend on mesh resolution, selected points and your chosen unit; use CAD or calibrated physical measurement for tighter tolerances.
Does viewing an STL check whether it is printable?
No. It is a visual inspection tool, not a mesh validation service.
What should I use to check for holes or non-manifold geometry?
Use the Quality Checker and Watertight Checker.