463 pages · markdown twin on every one

QR code documentation

The reference we wanted to exist: what QR codes are, how the format actually works, what scans and what doesn't, and the exact numbers for printing them. 463 pages, no paywall, no email gate, and no reason to exaggerate — we have nothing to sell you.

Every page is also served as plain markdown at {path}.md for machines, and indexed in /llms.txt.

Keyless · runnable from the page

REST API reference

The reference, by subject

QR code basics35What a QR code is, how it works, why you would use one — and the cases where you shouldn't.

QR code specification and internals40The ISO/IEC 18004 machinery: versions, capacity, error correction, masks, encoding modes. Every number here is implemented and tested in our open-source core.

How to make, scan and use QR codes52Task guides. Each one ends with a working generator, prefilled.

QR code design and customisation39Colours, shapes, logos and frames — and the contrast and coverage limits past which a code stops scanning.

Printing QR codes44Sizes, DPI, substrates, inks and durability. The cluster where a wrong answer costs a print run.

Scanning and device compatibility35What scans what, from iPhone cameras to warehouse imagers.

QR code troubleshooting39Something isn't scanning. Find the cause, in order of likelihood.

QR code security and privacy28Quishing, malicious stickers, what a QR code can and cannot do to your phone, and what your generator can see.

QR code payments45UPI, PIX, EPC/SEPA, EMVCo and crypto payment codes — field by field, from the actual specs.

QR codes for ecommerce and retail31Packaging, labels, reviews, returns and loyalty — the offline-to-online loop.

QR codes for social media and marketing23Creator, campaign and out-of-home use, and what scan rates to actually expect.

QR codes for developers and AI agents44Generate QR codes from any language, decode them, verify them, and wire them into agents.

QR code reference tables8Capacity, module counts, error-correction blocks and size-by-distance — generated from the spec, not copied from a blog.

Also in the reference