What it is built on
The tool stands on open-source engines, each served from our own domain:
- Online 3D Viewer (MIT licence) handles import, export and the 3D view.
- OpenCascade through occt-import-js (LGPL, a separate WASM file) reads STEP and IGES.
- manifold-3d (Apache licence) does booleans and cutting.
- meshoptimizer (MIT) reduces triangles.
- gcode-preview (MIT) draws G-code, and Clipper (Boost licence) offsets polygons.
- The Google Draco decoder (Apache licence) unpacks compressed glTF.
The FDM slicer, the print-time estimate and the G-code to STL rebuild are our own code.
What you need to use it
A Chromium browser is enough; the tool is tested in Chrome 155 and at a 390 px phone width. There is no account to create and nothing to install, and the current version adds no watermark. Large models are limited by your computer's memory rather than by a rule of ours: above roughly 1–2 million triangles the tab may run out of it.
How the pages are written
Every statement about the tool on this site comes from a list of facts, and each fact is backed by an automated test of the app or the extension. On 18.10.2026 the app suite passed 149 of 149 tests and the extension suite 6 of 6, in headless Chrome 155. When a feature has not been tested, the page says so: texture display, Firefox and Safari, printing our G-code on a real machine. If you find a claim that does not hold for your file, that is a bug in our list, and we would rather fix the page than keep the claim.
Contact
Questions, bug reports and files that do not open: write to support@stlview.app. If a file fails, say which format and which program made it; please do not attach anything confidential.