About STL Viewer Online

STL Viewer Online started from a small irritation: every time we needed to look at an STL someone had sent, the options were to launch a two-gigabyte slicer, install a viewer nobody had updated since 2015, or upload the file to a website that would keep a copy. None of those is acceptable when the file is a client's part, a scan of a person, or a design you sell.

What we built

A 3D file viewer that does everything in the browser tab. The file is read from your device, parsed in memory and drawn with WebGL; there is no upload, no account and no server-side copy. Around the viewer we added the things people actually need before a print: dimensions, volume and a watertight check, repair that fixes normals and duplicates and reports open edges honestly, a print cost calculator, converters between STL and OBJ, OBJ, GLB, PLY or 3MF and STL, STL and GLB and binary and ASCII STL, and dedicated pages for OBJ, GLB, 3MF and PLY. It follows the same approach as our other tool, opencsvviewer.com, which does the same for spreadsheet exports.

Principles

• Your files stay yours. Nothing you open here leaves your device. You can verify it in the browser's network panel.
• Show the mesh as it is. No smoothing, no silent hole filling, no automatic rescaling. The viewer reports what the file contains and warns when something looks wrong; it does not guess on your behalf.
• Fast on any machine. Files of hundreds of MB open on a laptop, and the page works on phones and Chromebooks that have no slicer at all.
• Free, without tricks. No file-size limits, no watermarks, no sign-up walls.

How the site is funded

Through advertising and sponsor placements shown around the tool, never through your files. Ads are served by third parties who may use cookies; see the privacy policy. Sponsors are labelled as such.

Who makes it

STL Viewer Online is built and maintained by Nikhil Gautam, a software engineer who got tired of installing software to look at one file. Bug reports and feature requests go straight to him through the contact page; the tool is updated in small, frequent releases (the "Last updated" date on each page is real).

Technology

The site is a static site built with Astro, served from a global edge network. Rendering and the format loaders use the open-source Three.js library; the mesh analysis, repair, measurement and exporters are our own code. Everything runs as plain JavaScript and WebGL in your browser.

Get in touch

Found a file that does not open correctly, or want a feature (STEP and G-code are on the list)? Contact us; a sample file (with nothing confidential in it) is the fastest way to get a bug fixed.