If you've ever received an STL or 3MF file and had no idea how to open it without downloading a slicer or CAD tool, this guide is for you. STLViewer lets you preview any STL or 3MF file in your browser — no install, no account, no cost.

How to view an STL or 3MF file online

Step 1 — Go to STLViewer.online

Open stlviewer.online in any modern browser — Chrome, Firefox, Safari, or Edge. Works on desktop and mobile. No account or sign-up required.

Step 2 — Upload your file

Drag and drop your STL or 3MF file onto the upload zone, or click to browse your files. Files up to 20 MB are accepted. The file is parsed directly in your browser — nothing is sent to a server unless you explicitly choose to share.

Step 3 — Navigate the 3D model

Once the model loads, you can interact with it immediately:

Rotate: click and drag
Zoom: scroll wheel or pinch on mobile
Pan: right-click drag, or two-finger drag on mobile

Use the Fit button in the toolbar to frame the entire model, or Reset to return to the default view.

Step 4 — Switch material presets

Open the Materials panel to apply a preset from six categories: Metal (steel, copper, gold), Wood (oak, walnut, pine), Stone (granite, marble, concrete), Plastic, Ceramic, and solid colors. Textures project seamlessly onto any mesh — no UV mapping required.

Step 5 — Measure distances on the model

Activate the Measure tool from the toolbar. Click any two points on the model surface to place anchors and read the exact distance between them. Useful for verifying part dimensions without opening a slicer.

Step 6 — Download a screenshot

Click the Screenshot button to save a PNG of the current viewport, including the active material and lighting setup. Good for documentation, quick previews, or sharing a static image.

Step 7 — Share your model with a link

Click Upload to store the file, then set an expiry (1 hour to 7 days) and copy the share link or QR code. Anyone with the link can open the model in their browser — no software required on their end.

Supported file formats

STLViewer supports:

STL — both binary and ASCII variants. Binary STL is identified by its file structure, not the extension, so corrupted or mislabeled files are caught cleanly.
3MF — the modern replacement for STL. Multi-part assemblies are fully supported: individual components are listed in a side panel and can be exported as standalone STL files.

You can also attach supplementary files alongside the main model — images (PNG, JPG, WEBP, GIF) and text files (TXT, MD) that appear on the shared model page.

Is my file uploaded to a server?

Not unless you choose to share it. Local previews run entirely in your browser via WebGL. The file never leaves your device during a local preview.

If you click Upload to generate a share link, the file is stored on Cloudflare R2 for the duration you chose (up to 7 days), then permanently deleted. Share links are private — not indexed by search engines, not listed anywhere publicly.

Viewing STL files on mobile

Touch controls work exactly as expected:

One-finger drag: rotates the model
Pinch: zooms in or out
Two-finger drag: pans the camera

The layout adapts to phone and tablet screen sizes. All toolbar controls meet comfortable touch target sizes.

Free plan

All features described in this guide — preview, materials, measurement, screenshot, sharing — are available for free without an account. Anonymous uploads produce a unique share link valid for up to 7 days.

An optional account adds dashboard management, download tracking, and the ability to extend model expiry times.