Online STL Viewer
Free STL File Viewer
Open an STL file in your browser and inspect the triangle mesh before you print, convert or share it. Toggle face normals and open edge highlights to spot geometry problems early.
See your STL mesh before you slice it
An STL can look fine in a file list while still containing holes, duplicated triangles or a flipped surface. The online STL viewer renders the mesh and gives you a quick visual pass without installing CAD software.
What you can inspect
- Triangle surface: Rotate through the isometric preview to confirm the model shape and overall scale.
- Face normals: Keep the face layer on to see the triangle network and surface orientation.
- Open edges: Orange dashed edges show boundaries that may become holes or slicer errors.
- Next step: Send a healthy mesh to Convert from STL, or open Repair STL when the checker finds a fixable boundary.
Frequently Asked Questions
Can I view an STL file online for free?
Yes. Drop an STL file into the viewer to inspect its mesh in your browser. Supported files can be parsed locally without an account.
Does the STL viewer upload my file?
The local viewer parses supported STL files in your browser. Files up to 250 MB can be inspected without an account or upload.
What do open edges mean in an STL file?
An open edge belongs to only one triangle and usually indicates a hole or an unclosed surface. Review the highlighted edges before slicing.