How to make a 3D QR keychain

2026-09-01 · 5 min read

The keychain concentrates every tradeoff of a printed QR code: little room, lots of handling, and a ring that always pulls from the same spot. It can be done well, but three numbers need respecting.

The three numbers

1. 40 mm a side, minimum. With a short link, the code area comes out to about 34 mm and modules stay above 1.5 mm.
2. 3 mm thick. Less and it breaks at the hole; more and it's bulky in a pocket.
3. 3 mm of material around the hole. That's where every keychain that breaks, breaks.

What content fits

A link of up to about 30 characters. That covers social media profiles, short domains, tel: links and shortened links. It doesn't cover long addresses with parameters or long WiFi passwords.

If your link doesn't fit, you have three options: shorten it, make the keychain bigger (50-55 mm), or rethink the content (linking to your homepage instead of a specific internal page, for example).

Design

• Short text below the code: your name or handle. Helps anyone who can't scan.
• Rounded corners: more comfortable and less prone to chipping.
• Matte colors: shine on an object that moves around in a hand complicates scanning.
• An emoji in the center works great on gift keychains and automatically raises the error correction.

Printing

PETG, 3 perimeters, 25% infill, 0.2 mm layers. With those settings the keychain lasts for years. PLA works just as well as long as it doesn't end up on a car dashboard in summer: above roughly 55°C it deforms.

Print lying flat, code facing up, and use a filament-change pause at the base's height for the second color.