# Mes3D — Free Online STL and 3D Model Viewer

> Mes3D opens STL, OBJ, PLY, glTF/GLB, 3MF, FBX, DAE, 3DS, USDZ, AMF and STEP/STP files in the browser, with measurement and mesh analysis. Files are parsed locally and never uploaded.

Source: https://freestlviewer.com/

Mes3D is a free 3D model viewer that runs entirely in the browser. You open a
file, it renders immediately, and you can rotate, measure and analyse it. There
is no account, no upload step and no server-side processing — the file is
parsed by your own browser, so confidential geometry never leaves your machine.

## Supported formats

STL (both binary and ASCII), OBJ, PLY, glTF, GLB, 3MF, FBX, DAE (Collada), 3DS,
USDZ, AMF and STEP/STP. The format is detected automatically from the file. For glTF,
self-contained `.glb` files work best because external texture and buffer
references cannot be resolved from a local file. For USDZ, both ASCII (USDA)
and binary (USDC) packages are supported. STEP and STP CAD files are
tessellated in the browser with OpenCASCADE.

## What it does

- **Viewing.** Rotate, zoom and pan; preset front, back, left, right, top and
  bottom views; perspective or orthographic projection; wireframe mode;
  auto-rotate.
- **Dimensions.** Bounding-box width, height and depth, plus the triangle
  count.
- **Measurement.** Click two points on the surface to get the straight-line
  distance between them.
- **Mesh analysis.** Volume, surface area, estimated print weight,
  watertight/manifold status with an open-edge count, and overhang ratio.
- **Appearance.** Preset or custom background and model colours.
- **Snapshot.** Export the current view as a PNG.

## How the analysis is calculated

Volume uses the signed-tetrahedron method: for every triangle with corner
vectors a, b and c, the term `a · (b × c) / 6` is summed across the mesh.
Surface area is `0.5 · |u × v|` per triangle. Both assume millimetre units,
because STL itself stores no unit.

Watertightness is checked by welding vertices that fall on the same quantised
grid position — the grid scales with the bounding-box diagonal — and then
counting how many triangles use each undirected edge. An edge used once is an
open edge (a hole); an edge used more than twice is non-manifold.

Overhang ratio assumes a +Z build direction and counts the area-weighted
fraction of faces whose normal Z component is below `-sin(45°)`.

Estimated weight is the volume in cm³ multiplied by the material density, at
100 % infill: PLA 1.24 g/cm³, PETG 1.27, ABS 1.04 and standard resin 1.15. Real
prints use walls plus sparse infill, so this figure is an upper bound.

## What is free

Viewing 3D models on the website is free everywhere, with no account and no
limits. On a computer the measurement, mesh analysis, snapshot and appearance
tools are free as well. On phones and tablets those advanced tools open in the
Mes3D mobile apps for iOS and Android instead; the apps are free to download
and some of their features are paid.

## Privacy

Mes3D is 100 % client-side. There is no upload endpoint, no file storage and no
server-side rendering of your model. Once the page has loaded, it also works
offline.