SliceLoft

STL Viewer

Open an ASCII or binary STL, inspect the mesh from every angle, and check its size before printing.

Files stay on your device. No upload, no account, no ads.

Drop an .stl file here or click to choose

ASCII or binary STL · one file at a time · up to 50 MiB / 500,000 triangles

Try a 20 × 20 × 20 mm cube with 12 triangles.

STL has no unit field. Coordinates are displayed as millimeters (mm), without scaling. Confirm the intended size in your slicer.

Mouse: drag to rotate, scroll to zoom, Shift + drag to pan.Touch: drag to rotate, pinch to zoom, two-finger drag to pan.

How to view an STL file online

  1. Choose or drop one .stl file, or load the sample. ASCII and binary formats are detected automatically.
  2. Rotate, zoom and pan to inspect the geometry. Reset view fits all currently visible objects into the preview.
  3. Read the dimensions and triangle count. STL does not declare units, so confirm that the millimeter interpretation matches your model.

What this preview can show

The viewer accepts standard ASCII and binary STL up to 50 MiB and 500,000 triangles, using the same parser as STL to 3MF. Empty, incomplete or degenerate meshes are rejected. It does not check watertightness, repair geometry or prepare G-code.

Frequently asked questions

Are my files uploaded, and can I view them offline?

No file data is uploaded. Parsing and 3D rendering happen in your browser, with no account or ads. Local files also work offline after the page and its scripts have loaded. Loading a sample makes a request for a public sample on this site and needs a connection unless it is cached.

Which STL formats and file sizes are supported?

Standard ASCII and binary STL are supported, one file at a time, up to 50 MiB and 500,000 triangles. The same parser and limits are used by STL to 3MF. Empty files, incomplete records, invalid coordinates and zero-area triangles are rejected. Device memory may impose a lower practical limit.

Does the STL viewer display colors or materials?

No. Standard STL contains triangle geometry without standard color or material fields. Nonstandard binary color attributes are ignored. The preview uses a single display color and cannot recover missing materials or textures.

How is this different from a slicer?

This is a geometry viewer for rotation, size checks and triangle counts. It does not generate G-code, simulate printed layers, calculate print time, add supports, apply slicer modifiers or repair meshes. A preview does not guarantee that a model is printable; verify it in a slicer before printing.

Why are STL dimensions shown in millimeters?

STL has no unit field. The viewer treats coordinate values as millimeters without scaling or guessing the source unit. Dimensions are the mesh’s X × Y × Z bounding box. If your model was designed in inches or another unit, correct its scale in your modeling software or slicer.

Why does the viewer show one object for an STL with several parts?

One STL is treated as one mesh object, even if it contains separate shells or several ASCII solid sections. The viewer does not split connected components. The dimensions include all triangles and any gaps between parts; the triangle count covers the whole file.

Can I convert the STL after viewing it?

Use the Convert STL to 3MF link and select the file again in the converter. It creates a geometry-only 3MF with explicit millimeter units. It does not restore colors or print settings, and the file is still processed locally.