3D Quality Tools

InspectMesh

Free STL Tools for 3D Printing

InspectMesh checks STL files before slicing or printing, so you can understand mesh health, size and complexity before committing material and time.

STL tools

Free STL Viewer

Open an STL locally in your browser, inspect it in 3D and see its dimensions and triangle count.

Open STL Viewer

STL Quality Checker

Find common mesh problems before printing, including open edges, non-manifold geometry, duplicate triangles and orientation issues.

Check STL quality

STL Print Preflight Checker

Run mesh, size, printer-fit, sampled wall-thickness and volume checks together before slicing.

Run STL preflight

STL Repair Tool

Clean duplicate and degenerate triangles, and correct simple orientation issues before checking the STL again.

Clean an STL safely

STL Watertight Checker

Check whether an STL has a closed surface, open edges or possible holes.

Check watertightness

STL Manifold Checker

Check whether an STL is closed and manifold, with clear counts for open edges, non-manifold edges and separate shells.

Check STL topology

STL Dimensions Checker

Measure an STL, convert units, calculate proportional scaling and check whether it fits your printer.

Measure an STL file

STL Scale Tool

Resize an STL proportionally by percentage, target dimension, or an assumed unit conversion, then download it locally.

Scale an STL

STL Wall Thickness Checker

Estimate sampled wall thickness locally and identify areas that may need closer print-preparation review.

Check wall thickness

STL Overhang Checker

Highlight downward-facing geometry that exceeds your chosen overhang review threshold.

Check overhang risk

STL Splitter

Split a valid STL into two capped printable parts.

Split an STL

STL Volume Calculator

Calculate your model’s volume, convert units and estimate approximate material weight.

Calculate STL volume

STL Triangle Counter

Count triangles and understand mesh complexity before slicing or sharing.

Count STL triangles

STL File Size Reducer

Convert ASCII STL to binary locally or simplify a copy with clear before-and-after file and triangle counts.

Reduce STL file size

STL to 3MF Converter

Convert an STL into a basic 3MF locally and choose the unit for its existing coordinates.

Convert STL to 3MF

Choosing how to place a model before slicing? Use the 3D Print Orientation Planner.

Browse all 3D file tools

Which tool do I need?

STL tool FAQ

What is an STL file?

An STL describes a model surface as a set of triangles. It is common in 3D printing, but it does not reliably store design units.

Should I check an STL before slicing?

Yes. Open edges, non-manifold geometry and unexpected scale can lead to confusing slicer results.

Does a clean check guarantee a successful print?

No. Printer calibration, supports, material and slicer settings still affect the physical result.

Simple, browser-friendly tools for better 3D prints.