Opens what you download
STL, 3MF, OBJ, PLY, GLB, glTF, G-code, OFF and 3DS, also straight from a ZIP. Open from Files, email, chat apps or a Printables link.
3D file viewer · iPhone and Android
Open 3D files on your phone. Check them before you print.
Extrude opens STL, 3MF, OBJ and G-code files, measures them, cuts a section and estimates the print. Every file stays on your device.
Free. Listed as “STL Viewer”. No account. Or open a file in your browser.
15,000+models opened since September 2026
10file formats
28languages
0files uploaded, ever
Counted by the app’s anonymous counters: no IDs, no file names. Updated October 31, 2026.
The checks you would do on a computer
Most of them sit behind a subscription in other apps. In Extrude they are free.
Measure on the model
Tap two points to get the distance in millimetres. Points snap to corners and edge midpoints, so the number is the one you meant.
Section view
Slide a cut through the model to check wall thickness and hidden cavities before you print.
Print estimate
Weight, filament length, print time and cost from your own settings. Sliced 3MF projects show the slicer’s numbers next to it.
Print check
Holes in the surface, thin walls, overhangs that need supports, a small base, floating parts and whether it fits your printer’s bed.
AR at real size
Put the part on your desk at its true size to see if it fits. Then export it as STL, or share an image, a 360° turn or a story video.
Mission
Built from emails, kept on your device
Extrude is made by one developer. Nearly every feature in it started as a message from someone using it, and the app credits them by name. Files are never uploaded, because a viewer has no reason to see them.
- Measuring and a print time estimate came from one email.
- Opening models inside a ZIP came from another.
- PLY, OFF, 3DS, GLB and glTF support, STL export and AR came from the next ones.
Questions
Is Extrude free?
Yes. Every tool in the app is free: measuring, section view, print estimate, print check and AR. A small banner ad pays for development. There is no account and no subscription.
Are my files uploaded?
No. The app reads files on your phone and never uploads, renames or moves them. The web viewer on this site works the same way: files open inside your browser tab.
Why is the app called STL Viewer on the stores?
That was its first name, and it is what people search for. Extrude is the name of the project behind it; the store listing will follow.
Which phones does it run on?
iPhone and iPad through the App Store, and Android phones and tablets through Google Play.
Does it work offline?
Yes. Opening, measuring and all the checks run on the device. Only opening a model from a web link needs a connection.
Can I open a file without installing anything?
Yes. Use the web viewer on this site from any browser with WebGL. It shows the model, its size, volume and triangle count.