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STL viewer

Drop an STL file below to view it in 3D. It opens inside your browser: the file is not uploaded anywhere. You get the model size in millimetres, its volume and the triangle count. To open STL files on an iPhone or Android phone, the free Extrude app does the same offline and adds measuring, section view and a print estimate.

Drop a 3D file here

STL, 3MF, OBJ, PLY, GLB or G-code. The file opens in this browser tab and is not uploaded.

File
–
Size (mm)
–
Volume
–
Triangles
–

Measure it, cut a section, estimate the print

The free Extrude app does this on your phone, offline. Listed as “STL Viewer”.

Download on the App StoreGet it on Google Play

What is an STL file?

STL is the most common file for 3D printing. It describes only the surface of a model, as a list of triangles. There is no colour, no material and no unit: almost every program treats the numbers as millimetres.

STL files come in two kinds. Binary STL is compact and is what most CAD tools export. ASCII STL is plain text and several times larger. The viewer reads both.

How to use this viewer

  1. Drop the file on the dark area, or press Choose file.
  2. Drag to rotate, scroll or pinch to zoom, right-drag or two-finger drag to pan.
  3. Read the size, volume and triangle count under the view. Use Wireframe to see the mesh.

Opening STL files on a phone

On iPhone, open an STL from Files, Mail, WhatsApp or Safari and choose Extrude (listed as STL Viewer). On Android, tap the file and pick the app, or open it from inside the app. STL files inside a ZIP open too.

Download on the App StoreGet it on Google Play

Questions

Is my STL file uploaded?

No. The viewer reads the file with your browser and draws it on your own device. No part of the file is sent to a server, and closing the tab removes it.

What unit does an STL file use?

STL has no unit field. Nearly all slicers and CAD tools read the numbers as millimetres, so the viewer shows sizes in mm. If a part looks 25.4 times too small, it was exported in inches.

How do I open an STL file on my phone?

Install Extrude (STL Viewer on the App Store and Google Play), then open the file from Files, email or a chat app and choose the app. It works offline and the file stays on the phone.

Why does my STL look hollow or broken?

Some faces point the wrong way or the mesh has holes. That often happens with scans and with files exported from modelling tools without a solid check. The Extrude app has a print check that counts open edges before you slice.

Other viewers

Every page opens every format. These cover what is different about each one.

3MF viewerOBJ viewerG-code viewerPLY viewerGLB viewer