Do my files get uploaded?

No. Everything runs in your browser. The file never leaves your computer, so it works for client files and unreleased designs too.

How big a file can it open?

Files around 100 MB open fine on a normal laptop. Very big scans can be slow on phones.

There are gaps in the surface. Many slicers patch small ones on their own; if yours complains, try our STL repair tool.

All tools / STL viewer

Open any STL to look it over before you print. You also get its real size, volume and a quick check for holes.

Good to know

Size is in millimetres, the unit slicers assume. If it says 0.1 × 0.2 × 0.1, the file was probably made in metres.
Triangles tells you how detailed it is. Under a million is fine for most printers and phones. Huge scans can be slow to slice.
Volume is the solid amount of plastic at 100% infill. It only shows when the mesh is closed.
Watertight means there are no gaps. Slicers like that, and many can't print without it.

STL stores the shape as triangles and nothing else: no colour, no unit, no settings. That's why every printer and slicer can read it.

Checked October 2026

Do my files get uploaded?: No. Everything runs in your browser. The file never leaves your computer, so it works for client files and unreleased designs too.
How big a file can it open?: Files around 100 MB open fine on a normal laptop. Very big scans can be slow on phones.
What does "not watertight" mean for my print?: There are gaps in the surface. Many slicers patch small ones on their own; if yours complains, try our STL repair tool.