How to make a QR code keychain
- Replace the example with your own link: an Instagram profile, a link-in-bio page, a digital business card or a phone number page.
- The keychain base is already chosen, with a loop at the top. Pick a look: the print plaque is the most reliable, bricks and jelly are the most fun.
- Leave the printed width at 40 mm, or go wider if the scan test or the size note says the modules are too small.
- Download the STL for a single-nozzle printer (the print guide tells you the layer to change filament at), or the 3MF for a multi-color printer.
Printing tips for small codes
A keychain is about as small as a 3D printed QR code gets, so the details matter more than on a sign. Keep the quiet zone at two modules or more: the loop sits outside it, so it never touches the code. Print with the code facing up and a light base: dark modules on a light plate read best, and matte filament reflects less than silk. If the corners of the modules round off, lower the print speed for the top layers or use a 0.2 mm nozzle.
Test the finished keychain with two phones before you hand it out, and check the link on a phone too: a login-only page is no use to someone who scans your keys.
Keychain sizes for this code
The example link makes a version 3 code: 29 × 29 modules, 33 across with its quiet zone. A module under about 1.2 mm is hard to print cleanly with a 0.4 mm nozzle.
| Printed width | Module size | Prints cleanly? |
|---|---|---|
| 30 mm | 0.91 mm | No: shorten the link |
| 35 mm | 1.06 mm | With a 0.2–0.3 mm nozzle |
| 40 mm | 1.21 mm | Yes |
| 50 mm | 1.52 mm | Yes |