Free Online STL Viewer
Open an STL file in your browser — nothing to install, nothing uploaded. Check its size, measure it, cut through it and repair it before you print.
What it opens
- Binary and ASCII STL, from any CAD program or slicer
- The other formats the viewer reads as well: STEP, IGES, STL, OBJ, glTF, 3MF, FBX, PLY, COLLADA, 3DS, USD, Rhino 3DM, VRML
- All in your browser — the file never leaves your computer, and there is no size limit set by a server
Check it before you print
- Size, bounding box, triangle and vertex count
- Surface area, volume, and the mass for a material such as PLA
- Measure between any two points, in mm or inches
- Section view: slide a clipping plane through the part
- Wireframe and edge views, orthographic or perspective
STL has no units
An STL file stores bare numbers, not millimetres or inches. The viewer reads them as millimetres, as most CAD and slicer exports mean them, and shows the size that gives. If a part comes out 25.4× too small, read the file as inches under Source units; scale it there too, and the export writes the unit you pick.
Fix a broken mesh
Repair welds duplicate vertices, drops degenerate triangles and makes the mesh manifold, and says how many edges were non-manifold before. Decimate lowers the triangle count for a lighter file; Diff compares two versions of a part as a colour map.
Convert an STL
The viewer exports to STL, OBJ, PLY, glTF, GLB, USDZ, 3MF. Or go straight to a converter:
Frequently asked questions
Is the STL viewer free? Do I need an account?
It is free and needs no account or install. Open the page and drop the file.
Is my STL file uploaded?
No. The file is read by your browser on your computer; nothing is sent to a server.
Does it open binary and ASCII STL?
Both. Most exports are binary (smaller); ASCII STL from older tools opens the same way.
Why does my model look tiny or huge?
STL stores no unit. The viewer assumes millimetres; a part drawn in inches comes out 25.4× too small — choose inches under Source units, or scale it.
Can I open a STEP file too?
Yes — the same viewer opens STEP and IGES. The STEP viewer page explains what changes for CAD files.
Does it work on a phone or tablet?
Yes, in a mobile browser: drag with one finger to rotate, pinch to zoom.
Open your STL now
Drop it in the 3D viewer — 13 formats, measure, section, repair and export.
Open the 3D viewer