Everything about QR codes
Clear explanations, a diagram on every page, and real codes you can scan with your phone. Start with the fundamentals or jump to what you need.
Fundamentals
What a QR code is, how it works, and the words you will meet everywhere else.
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Do QR codes expire?
A QR code is a printed pattern. Nothing in it can run out, and no one can switch it off.
3 min read
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How QR codes work
A QR code is text stored as a grid of dark and light squares called modules.
3 min read
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QR code analytics explained
A dynamic code records each scan's time, the country from the phone's network address, and the device family from the browser's user agent. It never learns who scanned.
6 min read
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QR code glossary
Seventy-odd QR code terms, A to Z, each defined in a sentence or two.
13 min read
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QR codes vs barcodes
A 1D barcode stores a dozen digits in stripes and needs a laser or line scanner. A 2D code stores thousands of characters in a grid and a phone camera reads it.
6 min read
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Static vs dynamic QR codes
A static code stores the destination in the squares. It never expires and needs no account.
5 min read
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What is a QR code?
A QR code is a short piece of text, usually a web address, drawn as dark and light squares.
4 min read
Under the hood
Versions, capacity, error correction, encoding and masking, explained with pictures.
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Masking and Reed-Solomon in QR codes
A mask is a fixed pattern XORed over the data so the code has no big blank areas or fake finder patterns.
7 min read
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QR code encoding explained
Text is stored as a mode indicator, a character count, then the data bits.
8 min read
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QR code error correction explained
Error correction adds spare codewords so a scanner can repair modules it read wrongly.
4 min read
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QR code versions and capacity
There are 40 versions. Version 1 is 21 by 21 modules; each step adds 4 a side up to 177 at version 40.
5 min read
History and culture
From a Toyota parts factory in 1994 to payments, protests and the Moon.
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Other 2D codes: Data Matrix, Aztec and PDF417
Data Matrix, Aztec, PDF417 and MaxiCode are open ISO standards older than or contemporary with the QR code, each dominant in one niche.
5 min read
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The history of QR codes
Masahiro Hara's two-person team at Denso released the QR code in 1994 to track car parts; the finder pattern came from a Go board.
6 min read
Security and privacy
Quishing, sticker scams and what a trustworthy scanner does with your data.
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QR code accessibility
A QR code on its own excludes blind users, many wheelchair users and anyone without a smartphone.
5 min read
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QR code security: quishing, fake stickers and safe scanning
A QR code cannot infect a phone. The danger is the link or action it carries, which you cannot see until you scan.
5 min read
Standards and regulation
ISO 18004, GS1 Sunrise 2027, digital product passports, payment QR formats.
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Digital product passports and the QR code on the box
From 18 February 2027, EU batteries for vehicles and industry need a QR code opening a battery passport.
5 min read
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ISO/IEC 18004 explained: the QR code standard
ISO/IEC 18004 defines the QR code. Editions came in 2000, 2006, 2015 and 2024; a fifth is in draft.
7 min read
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Payment QR codes: EMVCo, UPI, PIX, Alipay and EPC
A payment QR code carries either the payee's details (merchant-presented) or a one-time token for the payer's account (consumer-presented).
6 min read
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QR code trademark and patents
Denso Wave patented the QR code but waived its rights for any code that follows the JIS and ISO standards. Nothing to pay.
4 min read
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QR code variants
The code your phone reads is QR Model 2, standardized as ISO/IEC 18004.
8 min read
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QR codes and digital identity
A QR code can carry a signed credential itself, or a one-time link that lets a verifier request one from your wallet.
5 min read
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QR codes in retail and the supply chain
GS1 Digital Link puts the product number, batch, expiry and serial into a web address that a QR code carries.
6 min read
Interesting QR codes
Records, art, adverts, films, stamps and other codes worth knowing about.
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Interesting QR codes: a gallery of records, art and oddities
The largest scannable QR code was a 29,000 square meter corn maze in Alberta; the smallest measures under 2 square micrometers.
6 min read
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QR code myths, tested
QR codes are not dead, cannot run out, do not expire and cannot hack a phone by themselves.
5 min read
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QR code statistics that can be sourced
India had 657.9 million UPI QR codes at the end of FY25, up 91.5% in a year (RBI data).
4 min read