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A QR code (an
initialism An acronym is a word or name formed from the initial components of a longer name or phrase. Acronyms are usually formed from the initial letters of words, as in ''NATO'' (''North Atlantic Treaty Organization''), but sometimes use syllables, as ...
for quick response code) is a type of
matrix barcode A barcode or bar code is a method of representing data in a visual, machine-readable form. Initially, barcodes represented data by varying the widths, spacings and sizes of parallel lines. These barcodes, now commonly referred to as linear or o ...
(or two-dimensional barcode) invented in 1994 by the Japanese company Denso Wave. A barcode is a machine-readable optical label that can contain information about the item to which it is attached. In practice, QR codes often contain data for a locator, identifier, or tracker that points to a website or application. QR codes use four standardized encoding modes (numeric, alphanumeric, byte/binary, and
kanji are the logographic Chinese characters taken from the Chinese family of scripts, Chinese script and used in the writing of Japanese language, Japanese. They were made a major part of the Japanese writing system during the time of Old Japanese ...
) to store data efficiently; extensions may also be used. The quick response system became popular outside the automotive industry due to its fast readability and greater storage capacity compared to standard UPC barcodes. Applications include product tracking, item identification, time tracking, document management, and general marketing. A QR code consists of black squares arranged in a square grid on a white background, including some
fiducial marker A fiducial marker or fiducial is an object placed in the field of view of an imaging system that appears in the image produced, for use as a point of reference or a measure. It may be either something placed into or on the imaging subject, or a m ...
s, which can be read by an imaging device such as a camera, and processed using
Reed–Solomon error correction Reed–Solomon codes are a group of error-correcting codes that were introduced by Irving S. Reed and Gustave Solomon in 1960. They have many applications, the most prominent of which include consumer technologies such as MiniDiscs, CDs, DVDs, B ...
until the image can be appropriately interpreted. The required data is then extracted from patterns that are present in both horizontal and vertical components of the image.


History

The QR code system was invented in 1994 by Masahiro Hara from the Japanese company Denso Wave. The initial design was influenced by the black and white pieces on a
Go board Go equipment refers to the board, stones (playing pieces), and bowls for the stones required to play the game of Go. The quality and materials used in making Go equipment varies considerably, and the cost varies accordingly from economical to ex ...
. Its purpose was to keep track of automotive parts manufactured by Denso, to replace several bar codes on each box, each of which had to be scanned separately.


Adoption

QR codes are now used in a much broader context, including both commercial tracking applications and convenience-oriented applications aimed at mobile-phone users (termed mobile tagging). QR codes may be used to display text to the user, to open a webpage on the user's device, to add a
vCard vCard, also known as VCF (Virtual Contact File), is a file format standard for electronic business cards. vCards can be attached to e-mail messages, sent via Multimedia Messaging Service (MMS), on the World Wide Web, instant messaging, NFC ...
contact to the user's device, to open a
Uniform Resource Identifier A Uniform Resource Identifier (URI) is a unique sequence of characters that identifies a logical or physical resource used by web technologies. URIs may be used to identify anything, including real-world objects, such as people and places, conc ...
(URI), to connect to a wireless network, or to compose an email or text message. There are a great many QR code generators available as software or as online tools that are either free, or require a paid subscription. The QR code has become one of the most-used types of two-dimensional code. During the month of June 2011, 14 million American mobile users scanned a QR code or a barcode. Some 58% of those users scanned a QR or barcode from their homes, while 39% scanned from retail stores; 53% of the 14 million users were men between the ages of 18 and 34. In September 2020, a survey found that 18.8 percent of consumers in the United States and United Kingdom strongly agreed that they had noticed an increase of QR code use since the then-active COVID-19 related restrictions had begun several months prior.


Standards

There are several standards that cover the encoding of data as QR codes: *October 1997AIM (Association for Automatic Identification and Mobility) International *January 1999 JIS X 0510 *June 2000
ISO ISO is the most common abbreviation for the International Organization for Standardization. ISO or Iso may also refer to: Business and finance * Iso (supermarket), a chain of Danish supermarkets incorporated into the SuperBest chain in 2007 * Iso ...
/
IEC The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and r ...
18004:2000 ''Information technologyAutomatic identification and data capture techniquesBar code symbologyQR code'' (now withdrawn)
Defines QR code models 1 and 2 symbols. *1 September 2006ISO/IEC 18004:2006 ''Information technologyAutomatic identification and data capture techniquesQR code 2005 bar code symbology specification'' (now withdrawn)
Defines QR code 2005 symbols, an extension of QR code model 2. Does not specify how to read QR code model 1 symbols, or require this for compliance. *1 February 2015ISO/IEC 18004:2015 ''InformationAutomatic identification and data capture techniquesQR Code barcode symbology specification''
Renames the QR Code 2005 symbol to QR Code and adds clarification to some procedures and minor corrections. At the
application layer An application layer is an abstraction layer that specifies the shared communications protocols and Interface (computing), interface methods used by Host (network), hosts in a communications network. An ''application layer'' abstraction is speci ...
, there is some variation between most of the implementations. Japan's NTT DoCoMo has established
de facto ''De facto'' ( ; , "in fact") describes practices that exist in reality, whether or not they are officially recognized by laws or other formal norms. It is commonly used to refer to what happens in practice, in contrast with ''de jure'' ("by la ...
standards for the encoding of URLs, contact information, and several other data types. The open-source "
ZXing The application Barcode Scanner is an Android app, from the open-source project ZXing (short for Zebra Crossing), that allows an Android device with imaging hardware (a built-in camera) to scan barcodes or 2D barcodes and retrieve the data ...
" project maintains a list of QR code data types.


Uses

QR codes have become common in consumer advertising. Typically, a
smartphone A smartphone is a portable computer device that combines mobile telephone and computing functions into one unit. They are distinguished from feature phones by their stronger hardware capabilities and extensive mobile operating systems, whic ...
is used as a QR code scanner, displaying the code and converting it to some useful form (such as a standard URL for a website, thereby obviating the need for a user to type it into a
web browser A web browser is application software for accessing websites. When a user requests a web page from a particular website, the browser retrieves its files from a web server and then displays the page on the user's screen. Browsers are used on ...
). QR code has become a focus of advertising strategy, since it provides a way to access a brand's website more quickly than by manually entering a URL. Beyond mere convenience to the consumer, the importance of this capability is that it increases the
conversion rate In electronic commerce, conversion marketing is marketing with the intention of increasing ''conversions—''that is, site visitors who are paying customers. Measures Conversion marketing attempts to solve low online conversions through optim ...
: the chance that contact with the advertisement will convert to a sale. It coaxes interested prospects further down the
conversion funnel In e-commerce, the conversion funnel is the journey a consumer takes through an Internet advertising or search system, navigating an e-commerce website, and finally making a purchase. The consumer is seen as being "converted" from a visitor to the ...
with little delay or effort, bringing the viewer to the advertiser's website immediately, whereas a longer and more targeted sales pitch may lose the viewer's interest. Although initially used to track parts in vehicle manufacturing, QR codes are used over a much wider range of applications. These include commercial tracking, entertainment and transport ticketing, product and loyalty marketing and in-store product labeling. Examples of marketing include where a company's discounted and percent discount can be captured using a QR code decoder which is a mobile app, or storing a company's information such as address and related information alongside its alpha-numeric text data as can be seen in Yellow Pages directories. They can also be used in storing personal information for use by organizations. An example of this is Philippines National Bureau of Investigation (NBI) where NBI clearances now come with a QR code. Many of these applications target mobile-phone users (via
mobile tagging Mobile tagging is the process of providing data read from tags for display on mobile devices, commonly encoded in a two-dimensional barcode, using the camera of a camera phone as the reader device. The contents of the tag code is usually a URL f ...
). Users may receive text, add a vCard contact to their device, open a URL, or compose an
e-mail Electronic mail (email or e-mail) is a method of exchanging messages ("mail") between people using electronic devices. Email was thus conceived as the electronic ( digital) version of, or counterpart to, mail, at a time when "mail" meant ...
or text message after scanning QR codes. They can generate and print their own QR codes for others to scan and use by visiting one of several pay or free QR code-generating sites or apps. Google had an
API An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how ...
, now deprecated, to generate QR codes, and apps for scanning QR codes can be found on nearly all smartphone devices. QR codes storing addresses and URLs may appear in magazines, on signs, on buses, on business cards, or on almost any object about which users might want information. Users with a camera phone equipped with the correct reader application can scan the image of the QR code to display text, contact information, connect to a
wireless network A wireless network is a computer network that uses wireless data connections between network nodes. Wireless networking is a method by which homes, telecommunications networks and business installations avoid the costly process of introducing c ...
, or open a web page in the phone's browser. This act of linking from physical world objects is termed hardlinking or
object hyperlinking Object hyperlinking is a term that refers to extending the Internet to objects and locations in the real world. Object hyperlinking aims to extend the Internet to the physical world by attaching tags with URLs to tangible objects or locations. Thes ...
. QR codes also may be linked to a location to track where a code has been scanned. Either the application that scans the QR code retrieves the geo information by using GPS and cell tower triangulation (aGPS) or the URL encoded in the QR code itself is associated with a location. In 2008, a Japanese stonemason announced plans to engrave QR codes on gravestones, allowing visitors to view information about the deceased, and family members to keep track of visits. Psychologist
Richard Wiseman Richard J. Wiseman (born 17 September 1966) is a Professor of the Public Understanding of Psychology at the University of Hertfordshire in the United Kingdom. He has written several psychology books. He has given keynote addresses to The Royal ...
was one of the first authors to include QR codes in a book, in '' Paranormality: Why We See What Isn't There'' (2011). QR codes have been incorporated into currency. In June 2011, The
Royal Dutch Mint The Royal Dutch Mint (''Koninklijke Nederlandse Munt'', abbreviated ''KNM'') based in Houten, the Netherlands, is a company owned by Heylen Group. It was established and previously owned by the Dutch state. History On 17 September 1806, when The ...
(''Koninklijke Nederlandse Munt'') issued the world's first official coin with a QR code to celebrate the centenary of its current building and premises. The coin can be scanned by a smartphone and originally linked to a special website with contents about the historical event and design of the coin. In 2014, the Central Bank of Nigeria issued a 100-naira banknote to commemorate its centennial, the first banknote to incorporate a QR code in its design. When scanned with an internet-enabled mobile device, the code goes to a website which tells the centenary story of Nigeria. In 2015, the
Central Bank of the Russian Federation The Central Bank of the Russian Federation (CBR; ), doing business as the Bank of Russia (russian: Банк России}), is the central bank of the Russian Federation. The bank was established on July 13, 1990. The predecessor of the bank can ...
issued a 100-rubles note to commemorate the
annexation of Crimea by the Russian Federation In February and March 2014, Russia invaded and subsequently annexed the Crimean Peninsula from Ukraine. This event took place in the aftermath of the Revolution of Dignity and is part of the wider Russo-Ukrainian War. The events in Kyiv th ...
. It contains a QR code into its design, and when scanned with an internet-enabled mobile device, the code goes to a website that details the historical and technical background of the commemorative note. In 2017, the
Bank of Ghana The Bank of Ghana ( BoG) is the central bank of Ghana. It is located in Accra and was formed in 1957. The bank is active in developing financial inclusion policy and is a member of thAlliance for Financial Inclusion History The Central Ban ...
issued a 5-cedis banknote to commemorate 60 years of Central Banking in Ghana, and contains a QR code in its design, which when scanned with an internet-enabled mobile device, that code goes to the official Bank of Ghana website. Credit card functionality is under development. In September 2016, the Reserve Bank of India (RBI) launched the eponymously named Bharat QR, a common QR code jointly developed by all the four major card payment companies – National Payments Corporation of India that runs
RuPay RuPay ''(portmanteau of Rupee and Payment)'' is an Indian multinational financial services and payment service system, conceived and launched by the National Payments Corporation of India (NPCI) on 26 March 2012. It was created to fulfil th ...
cards along with MasterCard, Visa and American Express. It will also have the capability of accepting payments on the unified payments interface (UPI) platform.


Augmented reality

QR codes are used in some
augmented reality Augmented reality (AR) is an interactive experience that combines the real world and computer-generated content. The content can span multiple sensory modalities, including visual, auditory, haptic, somatosensory and olfactory. AR can be de ...
systems to determine the positions of objects in 3-dimensional space.


Displaying multimedia contents

QR codes also used to direct users to specific multimedia content (such as videos, audios, images, documents and any type of content accessible from the web). This type of QR code is called "Multimedia QR code".


Mobile operating systems

QR codes can be used on various mobile device operating systems. iPhones running on iOS 11 and higher and some Android devices can natively scan QR codes without downloading an external app. The camera app is able to scan and display the kind of QR code (only on iPhone) along with the link (both on Android and iPhone). These devices support
URL redirection URL redirection, also called URL forwarding, is a World Wide Web technique for making a web page available under more than one URL address. When a web browser attempts to open a URL that has been redirected, a page with a different URL is opened ...
, which allows QR codes to send
metadata Metadata is "data that provides information about other data", but not the content of the data, such as the text of a message or the image itself. There are many distinct types of metadata, including: * Descriptive metadata – the descriptive ...
to existing applications on the device. Many paid or free apps are available with the ability to scan the codes and hard-link to an external URL.


Virtual stores

QR codes have been used to establish "virtual stores", where a gallery of product information and QR codes is presented to the customer, e.g. on a train station wall. The customers scan the QR codes, and the products are delivered to their homes. This use started in South Korea, and Argentina, but is currently expanding globally. Walmart, Procter & Gamble and Woolworths have already adopted the Virtual Store concept.


QR code payment

QR codes can be used to store bank account information or credit card information, or they can be specifically designed to work with particular payment provider applications. There are several trial applications of QR code payments across the world. In developing countries like China, India and Bangladesh QR code payment is a very popular and convenient method of making payments. Since
Alipay Alipay () is a third-party mobile and online payment platform, established in Hangzhou, China in February 2004 by Alibaba Group and its founder Jack Ma. In 2015, Alipay moved its headquarters to Pudong, Shanghai, although its parent company An ...
designed a QR code payment method in 2011, mobile payment has been quickly adopted in China. As of 2018, around 83% of all payments were made via mobile payment. In November 2012, QR code payments were deployed on a larger scale in the
Czech Republic The Czech Republic, or simply Czechia, is a landlocked country in Central Europe. Historically known as Bohemia, it is bordered by Austria to the south, Germany to the west, Poland to the northeast, and Slovakia to the southeast. The ...
when an open format for payment information exchange – a
Short Payment Descriptor Short Payment Descriptor (SPAYD, SPD) is a compact data format for an easy exchange of payment information using modern electronic channels, such as smart phones or NFC devices. Practically, the format is being deployed in the Czech Republic (wher ...
 – was introduced and endorsed by the Czech Banking Association as the official local solution for QR payments. In 2013, the European Payment Council provided guidelines for the
EPC QR code The European Payments Council Quick Response Code guidelines define the content of a QR code that can be used to initiate SEPA credit transfer (SCT). It contains all the necessary information in clear text. These QR code guidelines are used on many ...
enabling SCT initiation within the
Eurozone The euro area, commonly called eurozone (EZ), is a currency union of 19 member states of the European Union (EU) that have adopted the euro (€) as their primary currency and sole legal tender, and have thus fully implemented EMU policies ...
. In 2017, Singapore created a taskforce including their Government Agencies such as the Monetary Authority of Singapore and Infocomm Media Development Authority to spearhead a system for e-payments using standardized QR code specifications. These specific dimensions are specialized for Singapore’s market. The e-payment system, Singapore Quick Response Code (SGQR), essentially merges various QR codes into one label which can be used by both parties in the payment system. This allows for various banking apps to facilitate payments between multiple customers and a merchant that displays the single QR code. A single SDQR label contains e-payments and combines multiple payment options. Once consumers spot the SGQR label, they will be able to scan it and see which payment options the merchant accepts.  The SGQR scheme is co-owned by MAS and IMDA.


Website login

QR codes can be used to log into websites: a QR code is shown on the login page on a
computer screen A computer monitor is an output device that displays information in pictorial or textual form. A discrete monitor comprises a visual display, support electronics, power supply, housing, electrical connectors, and external user controls. The di ...
, and when a registered user scans it with a verified smartphone, they will automatically be logged in. Authentication is performed by the smartphone which contacts the server. Google tested such a login method in January 2012.


Mobile ticket

There is a system whereby a QR code can be displayed on a device such as a smartphone and used as an
admission ticket A ticket is a voucher that indicates that an individual is entitled to admission to an event or establishment such as a theatre, amusement park, or tourist attraction, or has a right to travel on a vehicle, such as with an airline ticket, ...
. Its use is common for
J1 League The , known as the for sponsorship reasons, is the top level of the system. Founded in 1992, it is one of the most successful leagues in Asian club football. Contested by 18 clubs, it operates on a system of promotion and relegation with the J ...
and
Nippon Professional Baseball or NPB is the highest level of baseball in Japan. Locally, it is often called , meaning ''Professional Baseball''. Outside Japan, it is often just referred to as "Japanese baseball". The roots of the league can be traced back to the formation ...
tickets in Japan. In some cases, rights can be transferred via the Internet.


Restaurant ordering

Restaurants can present a QR code near the front door or at the table allowing guests to view an online menu, or even redirect them to an online ordering website or app, allowing them to order and/or possibly pay for their meal without having to use a cashier or waiter. QR codes can also link to daily or weekly specials that are not printed on the standardized menus, and enable the establishment to update the entire menu without needing to print copies. At table-serve restaurants, QR codes enable guests to order and pay for their meals without a waiter involved – the QR code contains the table number so servers know where to bring the food. This application has grown especially since the need for social distancing during the 2020 COVID-19 pandemic prompted reduced contact between service staff and customers.


Joining a Wi‑Fi network

By specifying the SSID, encryption type, password/passphrase, and if the SSID is hidden or not, mobile device users can quickly scan and join networks without having to manually enter the data. A MeCard-like format is supported by Android and iOS 11+. * Common format: WIFI:S:;T:;P:;H:;; * Sample: WIFI:S:MySSID;T:WPA;P:MyPassW0rd;;


Funerary use

A QR code can link to an
obituary An obituary ( obit for short) is an article about a recently deceased person. Newspapers often publish obituaries as news articles. Although obituaries tend to focus on positive aspects of the subject's life, this is not always the case. Ac ...
and can be placed on a
headstone A headstone, tombstone, or gravestone is a stele or marker, usually stone, that is placed over a grave. It is traditional for burials in the Christian, Jewish, and Muslim religions, among others. In most cases, it has the deceased's name, da ...
. In 2008, Ishinokoe in Yamanashi Prefecture, Japan began to sell tombstones with QR codes produced by IT DeSign, where the code leads to a virtual grave site of the deceased. Other companies, such as Wisconsin-based Interactive Headstones, have also begun implementing QR codes into tombstones. In 2014, the Jewish Cemetery of La Paz in Uruguay began implementing QR codes for tombstones.


Electronic authentication

QR codes are also used to generate time-based one-time passwords (TOTP) for
electronic authentication Electronic authentication is the process of establishing confidence in user identities electronically presented to an information system. Digital authentication, or e-authentication, may be used synonymously when referring to the authentication proc ...
.


Loyalty programs

QR codes have been used by various retail outlets that have
loyalty program A loyalty program is a marketing strategy designed to encourage customers to continue to shop at or use the services of a business associated with the program. Today, such programs cover most types of commerce, each having varying features and ...
s. Sometimes these programs are accessed with an app that is loaded onto a phone and includes a process triggered by a QR code scan. The QR codes for loyalty programs tend to be found printed on the
receipt A receipt (also known as a packing list, packing slip, packaging slip, (delivery) docket, shipping list, delivery list, bill of the parcel, manifest, or customer receipt) is a document acknowledging that a person has received money or propert ...
for a purchase or on the products themselves. Users in these schemes collect award points by scanning a code.


Counterfeit detection

Serialised QR codes have been used by brands and governments to let consumers, retailers and distributors verify the authenticity of the products and help with detecting counterfeit products, as part of a
brand protection Brand protection is the process and set of actions that a right holder undertakes to prevent third parties from using its intellectual property without permission, as this may cause loss of revenue and, usually more importantly, destroys brand eq ...
program. However, the security level of a regular QR Code is limited since QR Codes printed on original products are easily reproduced on fake products, even though the analysis of data generated as a result of QR Code scanning can be used to detect counterfeiting and illicit activity. A higher security level can be attained by embedding a
digital watermark A digital watermark is a kind of marker covertly embedded in a noise-tolerant signal such as audio, video or image data. It is typically used to identify ownership of the copyright of such signal. "Watermarking" is the process of hiding digital inf ...
or
copy detection pattern A copy detection pattern (CDP) or graphical code is a small Randomness, random or Pseudorandomness, pseudo-random digital image which is printed on documents, labels or products for counterfeit detection. Authentication is made by scanning th ...
into the image of the QR Code. This makes the QR Code more secure against counterfeiting attempts, and fake products which contain a counterfeit QR Code can be detected by scanning the secure QR Code with a specific app (even though the QR Code message itself is valid). The treaty regulating
apostille The Convention of 5 October 1961 Abolishing the Requirement of Legalisation for Foreign Public Documents, also known as the Apostille Convention, is an international treaty drafted by the Hague Conference on Private International Law (HCCH). ...
s (documents bearing a seal of authenticity), has been updated to allow for the issuance of digital apostilles by countries; a digital apostille is a PDF document with a
cryptographic signature A digital signature is a mathematical scheme for verifying the authenticity of digital messages or documents. A valid digital signature, where the prerequisites are satisfied, gives a recipient very high confidence that the message was created b ...
containing a QR code for a canonical URL of the original document, allowing users to verify the apostille from a printed version of the document.


Product tracing

Different studies have been made to assess the effectiveness of QR codes as a means of conveying labelling information and their use as part of a food traceability system. In a field experiment, it was found that when provided free access to a smartphone with QR Code scanning app, 52.6% of participants would use it to access labelling information. A study made in South Korea showed that consumers appreciate QR code used in food traceability system, as they provide detailed information about food, as well as information that helps them in their purchasing decision. If QR Codes are serialised, consumers can access a web page showing the supply chain for each ingredient, as well as information specific to each related batch, including meat processors and manufacturers, which helps address the concerns they have about the origin of their food.


COVID-19 pandemic

After the
COVID-19 pandemic The COVID-19 pandemic, also known as the coronavirus pandemic, is an ongoing global pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The novel virus was first identif ...
began spreading, QR codes began to be used as a "touchless" system to display information, show menus, or provide updated consumer information, especially in the hospitality industry. Restaurants replaced paper or laminated plastic menus with QR code decals on the table, which opened an online version of the menu. This prevented the need to dispose of single-use paper menus, or institute cleaning and sanitizing procedures for permanent menus after each use. Local television stations have also begun to utilize codes on local newscasts to allow viewers quicker access to stories or information involving the pandemic, including testing and immunization scheduling websites, or for links within stories mentioned in the newscasts overall. In several Australian states, patrons are required to scan QR codes at shops, clubs, supermarkets and other service and retail establishments on entry to assist
contact tracing In public health, contact tracing is the process of identifying persons who may have been exposed to an infected person ("contacts") and subsequent collection of further data to assess transmission. By tracing the contacts of infected individua ...
. Singapore,
Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia, at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the nort ...
, the United Kingdom and New Zealand use similar systems. QR codes are also present on COVID-19 vaccination certificates in places such as Canada, and the EU (EU Digital COVID certificate) where they can be scanned to verify the information on the certificate.


Design

Unlike the older, one-dimensional barcodes that were designed to be mechanically scanned by a narrow beam of light, a QR code is detected by a 2-dimensional digital
image sensor An image sensor or imager is a sensor that detects and conveys information used to make an image. It does so by converting the variable attenuation of light waves (as they pass through or reflect off objects) into signals, small bursts of curr ...
and then digitally analyzed by a programmed processor. The processor locates the three distinctive squares at the corners of the QR code image, using a smaller square (or multiple squares) near the fourth corner to normalize the image for size, orientation, and angle of viewing. The small dots throughout the QR code are then converted to binary numbers and validated with an error-correcting algorithm.


Storage

The amount of data that can be stored in the QR code symbol depends on the data type (''mode'', or input character set), version (1, ..., 40, indicating the overall dimensions of the symbol, i.e. 4 × version number + 17 dots on each side), and
error correction In information theory and coding theory with applications in computer science and telecommunication, error detection and correction (EDAC) or error control are techniques that enable reliable delivery of digital data over unreliable communica ...
level. The maximum storage capacities occur for version 40 and error correction level L (low), denoted by 40-L: Here are some sample QR code symbols: File:Qr-1.svg, Version 1 (21×21). Content: "Ver1" File:Qr-2.svg, Version 2 (25×25). Content: "Version 2" File:Qr-3.svg, Version 3 (29×29). Content: "Version 3 QR Code" File:Qr-4.svg, Version 4 (33×33). Content: "Version 4 QR Code, up to 50 char" File:Qr-code-ver-10.svg, Version 10 (57×57). Content: "VERSION 10 QR CODE, UP TO 174 CHAR AT H LEVEL, WITH 57X57 MODULES AND PLENTY OF ERROR CORRECTION TO GO AROUND. NOTE THAT THERE ARE ADDITIONAL TRACKING BOXES" (actually encoded in all capital letters). (Tracking boxes are more commonly called ''alignment patterns''.) File:QR_Code_Version_25.svg, Version 25 (117×117) Content: 1,269 characters of ASCII text describing QR Codes File:Qr-code-ver-40.svg, Version 40 (177×177) Content: "Version 40 QR Code can contain up to 1852 chars..." (and followed by four paragraphs of ASCII text describing QR Codes).


Error correction

QR codes use
Reed–Solomon error correction Reed–Solomon codes are a group of error-correcting codes that were introduced by Irving S. Reed and Gustave Solomon in 1960. They have many applications, the most prominent of which include consumer technologies such as MiniDiscs, CDs, DVDs, B ...
over the
finite field In mathematics, a finite field or Galois field (so-named in honor of Évariste Galois) is a field that contains a finite number of elements. As with any field, a finite field is a set on which the operations of multiplication, addition, subtr ...
\mathbb_, the elements of which are encoded as bytes of 8 bits; the byte b_7b_6b_5b_4b_3b_2b_1b_0 with a standard numerical value \textstyle\sum_^7 b_i 2^i encodes the field element \textstyle\sum_^7 b_i \alpha^i where \alpha \in \mathbb_ is taken to be a primitive element satisfying \alpha^8 + \alpha^4 + \alpha^3 + \alpha^2 + 1 = 0. The Reed–Solomon code uses one of 37 different polynomials over \mathbb_, with degrees ranging from 7 to 68, depending on how many error correction bytes the code adds. It is implied by the form of Reed–Solomon used ( systematic BCH view) that these polynomials are all on the form \prod_^ (x - \alpha^i), however the rules for selecting the degree n are specific to the QR standard. When discussing the Reed–Solomon code phase there is some risk for confusion, in that the QR ISO/IEC standard uses the term ''codeword'' for the elements of \mathbb_, which with respect to the Reed–Solomon code are
symbols A symbol is a mark, sign, or word that indicates, signifies, or is understood as representing an idea, object, or relationship. Symbols allow people to go beyond what is known or seen by creating linkages between otherwise very different conc ...
, whereas it uses the term ''block'' for what with respect to the Reed–Solomon code are the codewords. The number of data versus error correction bytes within each block depends on (i) the version (side length) of the QR symbol and (ii) the error correction level, of which there are four. The higher the error correction level, the less storage capacity. The following table lists the approximate error correction capability at each of the four levels: In larger QR symbols, the message is broken up into several Reed–Solomon code blocks. The block size is chosen so that no attempt is made at correcting more than 15 errors per block; this limits the complexity of the decoding algorithm. The code blocks are then interleaved together, making it less likely that localized damage to a QR symbol will overwhelm the capacity of any single block. Due to error correction, it is possible to create artistic QR codes with embellishments to make them more readable or attractive to the human eye, and to incorporate colors, logos, and other features into the QR code block; the embellishments are treated as errors, but the codes still scan correctly. It is also possible to design artistic QR codes without reducing the error correction capacity by manipulating the underlying mathematical constructs. Image processing algorithms are also used to reduce errors in QR-code.


Encoding

The format information records two things: the error correction level and the mask pattern used for the symbol. Masking is used to break up patterns in the data area that might confuse a scanner, such as large blank areas or misleading features that look like the locator marks. The mask patterns are defined on a grid that is repeated as necessary to cover the whole symbol. Modules corresponding to the dark areas of the mask are inverted. The format information is protected from errors with a
BCH code In coding theory, the Bose–Chaudhuri–Hocquenghem codes (BCH codes) form a class of cyclic error-correcting codes that are constructed using polynomials over a finite field (also called ''Galois field''). BCH codes were invented in 1959 ...
, and two complete copies are included in each QR symbol. The message dataset is placed from right to left in a zigzag pattern, as shown below. In larger symbols, this is complicated by the presence of the alignment patterns and the use of multiple interleaved error-correction blocks. File:QR Format Information.svg, Meaning of format information. In the above figure, the format information is protected by a (15,5) BCH code, which can correct up to 3 bit errors. The total length of the code is 15 bits, of which 5 are data bits (2 EC level + 3 mask pattern) and 10 are extra bits for error correction. The format mask for these 15 bits is: 01010000010010 Note that we map the masked values directly to its meaning here, in contrast to image 4 "Levels & Masks" where the mask pattern numbers are the result of putting the 3rd to 5th mask bit, 01 over the 3rd to 5th format info bit of the QR code. File:QR Character Placement.svg, Message placement within a QR symbol. The message is encoded using a (255,249) Reed Solomon code (shortened to (24,18) code by using "padding") which can correct up to 3 byte errors. File:QR Ver3 Codeword Ordering.svg, Larger symbol illustrating interleaved blocks. The message has 26 data bytes and is encoded using two Reed-Solomon code blocks. Each block is a (255,233) Reed Solomon code (shortened to (35,13) code), which can correct up to 11 byte errors in a single burst, containing 13 data bytes and 22 "parity" bytes appended to the data bytes. The two 35-byte Reed-Solomon code blocks are interleaved so it can correct up to 22 byte errors in a single burst (resulting in a total of 70 code bytes). The symbol achieves level H error correction. The general structure of a QR encoding is as a sequence of 4 bit indicators with payload length dependent on the indicator mode (e.g. byte encoding payload length is dependent on the first byte).
:Note: :* Character Count Indicator depends on how many modules are in a QR code (Symbol Version). :* ECI Assignment number Size: :** 8 × 1 bits if ECI Assignment Bitstream starts with '0' :** 8 × 2 bits if ECI Assignment Bitstream starts with '10' :** 8 × 3 bits if ECI Assignment Bitstream starts with '110'
Four-bit indicators are used to select the encoding mode and convey other information. Encoding modes can be mixed as needed within a QR symbol. (e.g., a url with a long string of alphanumeric characters ) Mode Indicator Mode bitstream ] --> Mode Indicator Mode bitstream ] --> etc... --> 0000 End of message (Terminator) After every indicator that selects an encoding mode is a length field that tells how many characters are encoded in that mode. The number of bits in the length field depends on the encoding and the symbol version. Alphanumeric encoding mode stores a message more compactly than the byte mode can, but cannot store lower-case letters and has only a limited selection of punctuation marks, which are sufficient for rudimentary
web address A Uniform Resource Locator (URL), colloquially termed as a web address, is a reference to a web resource that specifies its location on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identifie ...
es. Two characters are coded in an 11-bit value by this formula: :V = 45 × C1 + C2 This has the exception that the last character in an alphanumeric string with an odd length is read as a 6-bit value instead.


Decoding example

The following images offer more information about the QR code. File:QRCode-1-Intro.png, 1 – Introduction File:QRCode-2-Structure.png, 2 – Structure File:QRCode-3-Layout,Encoding.png, 3 – Layout & Encoding File:QRCode-4-Levels,Masks.png, 4 – Levels & Masks File:QRCode-5-Protocols.png, 5 – Protocols


Variants


Model 1

''Model 1 QR code'' is an older version of the specification. It is visually similar to the widely seen model 2 codes, but lacks alignment patterns. Differences are in the bottom right corner, and in the midsections of the bottom and right edges are additional functional regions. File:QR Code Model 1 Example.svg, Model 1 QR code example File:Model 1 QR Version 2 Layout.svg, Model 1 QR code functional regions


Micro QR code

Micro QR code is a smaller version of the QR code standard for applications where symbol size is limited. There are four different versions (sizes) of Micro QR codes: the smallest is 11×11 modules; the largest can hold 35 numeric characters. File:Micro QR Example.svg, Micro QR code example File:Micro QR Version 3M Layout.svg, Micro QR code functional regions


IQR code

IQR Code is an alternative to existing QR codes developed by Denso Wave. IQR codes can be created in square or rectangular formations; this is intended for situations where a rectangular barcode would otherwise be more appropriate, such as cylindrical objects. IQR codes can fit the same amount of information in 30% less space. There are 61 versions of square IQR codes, and 15 versions of rectangular codes. For squares, the minimum size is 9 × 9 modules; rectangles have a minimum of 19 × 5 modules. IQR codes add error correction level S, which allows for 50% error correction. IQR Codes have not yet been given an ISO/IEC specification, and only proprietary Denso Wave products can create or read IQR codes.


Secure QR code

Secure Quick Response (SQR) code is a QR code that contains a "private data" segment after the terminator instead of the specified filler bytes "ec 11". This private data segment must be deciphered with an encryption key. This can be used to store private information and to manage company's internal information. SQR codes have been developed by the FORUS Foundation to enable secure transactions, and published under a Creative Commons Licence. The SQR solution guarantees the integrity of the source data as well as the validity of the originating party. The payment instruction string is made up of the electronic instruction data from the scanned QR code appended with a SHA-2 cryptographic hash. The message digest can then be encrypted using the private key of the sender, which then creates a digital signature of the message. This signature validates the integrity of the data and the trustworthiness of the sender. This provides non-repudiation, confirming the identity of the sender, and that it has not been tampered with during transmission. By embedding the URL and all the variables required to perform shopping cart type e-commerce, bill payment and peer to peer payments, coupled with a digital certificate eliminates the possibility of spoofing, tampering, and man in the middle attacks.


Frame QR

Frame QR is a QR code with a "canvas area" that can be flexibly used. In the center of this code is the canvas area, where graphics, letters, and more can be flexibly arranged, making it possible to lay out the code without losing the design of illustrations, photos, etc.


HCC2D

Researchers have proposed a new High Capacity Colored 2-Dimensional (HCC2D) Code, which builds upon a QR code basis for preserving the QR robustness to distortions and uses colors for increasing data density (as of 2014 it is still in prototyping phase). The HCC2D code specification is described in details in Querini ''et al.'' (2014), while techniques for color classification of HCC2D code cells are described in detail in Querini and
Italiano Italian (''italiano'' or ) is a Romance language of the Indo-European language family that evolved from the Vulgar Latin of the Roman Empire. Together with Sardinian, Italian is the least divergent language from Latin. Spoken by about 85 m ...
(2014), which is an extended version of Querini and Italiano (2013). Introducing colors into QR codes requires addressing additional issues. In particular, during QR code reading only the brightness information is taken into account, while HCC2D codes have to cope with chromatic distortions during the decoding phase. In order to ensure adaptation to chromatic distortions which arise in each scanned code, HCC2D codes make use of an additional field: the Color Palette Pattern. This is because color cells of a Color Palette Pattern are supposed to be distorted in the same way as color cells of the Encoding Region. Replicated color palettes are used for training machine learning classifiers.


JAB code

JAB code (Just Another Barcode) is a color 2D matrix symbology made of color squares arranged in either square or rectangle grids. It was developed by Fraunhofer Institute SIT (Secure Information Technology). The code contains one primary symbol and optionally multiple secondary symbols. The primary symbol contains four finder patterns located at the corners of the symbol. The code uses either 4 or 8 colours. The 4 basic colours (cyan, magenta, yellow, black) are the 4 primary colours of the subtractive
CMYK color model The CMYK color model (also known as process color, or four color) is a subtractive color model, based on the CMY color model, used in color printing, and is also used to describe the printing process itself. The abbreviation ''CMYK'' refers ...
which is the most widely used system in industry for colour printing on a white base such as paper. The other 4 colours (blue, red, green, white) are secondary colours of the CMYK model and originate as an equal mixture of a pair of basic colours. The barcode is not subject to licensing and was submitted to ISO/IEC standardization as ISO/IEC 23634 expected to be approved at the beginning of 2021 and finalized in 2022. The software is
open-source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized sof ...
and published under the
LGPL The GNU Lesser General Public License (LGPL) is a free-software license published by the Free Software Foundation (FSF). The license allows developers and companies to use and integrate a software component released under the LGPL into their own ...
v2.1 license. The specification is freely available. Because the colour adds a third dimension to the two-dimensional matrix, a JAB code can contain more information in the same area compared to two-colour (black and white) codes – theoretically twice as much data for a 4 colour code and three times more for 8 colours assuming the same encoding algorithm. This can allow storage of an entire message in the barcode, rather than just storing partial data with a reference to a full message somewhere else (such as a link to a website), thus eliminating the need for additional always-available infrastructure beyond the printed barcode itself. It may be used to digitally sign encrypted digital version of printed legal documents, contracts and certificates (diplomas, training), medical prescriptions or provide product authenticity assurance to increase protection against counterfeits.


License

The use of QR code technology is freely licensed as long as users follow the standards for QR Code documented with JIS or
ISO ISO is the most common abbreviation for the International Organization for Standardization. ISO or Iso may also refer to: Business and finance * Iso (supermarket), a chain of Danish supermarkets incorporated into the SuperBest chain in 2007 * Iso ...
/
IEC The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and r ...
. Non-standardized codes may require special licensing. Denso Wave owns a number of patents on QR code technology, but has chosen to exercise them in a limited fashion. In order to promote widespread usage of the technology Denso Wave chose to waive its rights to a key patent in its possession for ''standardized'' codes only. In the US, the granted QR code patent is , and in Japan , both of which have expired. The European Patent Office granted patent to Denso Wave, which was then validated into French, UK, and German patents, all of which expired in March 2015. The text ''QR Code'' itself is a
registered trademark The registered trademark symbol, , is a typographic symbol that provides notice that the preceding word or symbol is a trademark or service mark that has been registered with a national trademark office. A trademark is a symbol, word, or word ...
and
wordmark __notoc__ A wordmark, word mark, or logotype, is usually a distinct text-only typographic treatment of the name of a company, institution, or product name used for purposes of identification and branding. Examples can be found in the graphic iden ...
of Denso Wave Incorporated. In UK, the trademark is registered as E921775, the term ''QR Code'', with a filing date of 3 September 1998. The UK version of the trademark is based on the Kabushiki Kaisha Denso (DENSO CORPORATION) trademark, filed as Trademark 000921775, the term ''QR Code'', on 3 September 1998 and registered on 16 December 1999 with the European Union OHIM (Office for Harmonization in the Internal Market). The U.S. Trademark for the term ''QR Code'' is Trademark 2435991 and was filed on 29 September 1998 with an amended registration date of 13 March 2001, assigned to Denso Corporation.


Risks

The only context in which common QR codes can carry executable data is the URL data type. These URLs may host
JavaScript JavaScript (), often abbreviated as JS, is a programming language that is one of the core technologies of the World Wide Web, alongside HTML and CSS. As of 2022, 98% of Website, websites use JavaScript on the Client (computing), client side ...
code, which can be used to exploit vulnerabilities in applications on the host system, such as the reader, the web browser or the image viewer, since a reader will typically send the data to the application associated with the data type used by the QR code. In the case of no software exploits, malicious QR codes combined with a permissive reader can still put a computer's contents and user's privacy at risk. This practice is known as "attagging", a
portmanteau A portmanteau word, or portmanteau (, ) is a blend of words. They are easily created and can be affixed over legitimate QR codes. On a smartphone, the reader's permissions may allow use of the camera, full Internet access, read/write contact data,
GPS The Global Positioning System (GPS), originally Navstar GPS, is a Radionavigation-satellite service, satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of t ...
, read browser history, read/write local storage, and global system changes. Risks include linking to dangerous web sites with browser exploits, enabling the microphone/camera/GPS, and then streaming those feeds to a remote server, analysis of sensitive data (passwords, files, contacts, transactions), and sending email/
SMS Short Message/Messaging Service, commonly abbreviated as SMS, is a text messaging service component of most telephone, Internet and mobile device systems. It uses standardized communication protocols that let mobile devices exchange short text ...
/IM messages or packets for
DDoS In computing, a denial-of-service attack (DoS attack) is a cyber-attack in which the perpetrator seeks to make a machine or network resource unavailable to its intended users by temporarily or indefinitely disrupting services of a host connec ...
as part of a
botnet A botnet is a group of Internet-connected devices, each of which runs one or more bots. Botnets can be used to perform Distributed Denial-of-Service (DDoS) attacks, steal data, send spam, and allow the attacker to access the device and its conn ...
, corrupting privacy settings, stealing identity, and even containing malicious logic themselves such as JavaScript or a virus. These actions could occur in the background while the user is only seeing the reader opening a seemingly harmless web page. In Russia, a malicious QR code caused phones that scanned it to send premium texts at a fee of $6 each. QR codes have also been linked to scams in which stickers are placed on
parking meters A parking meter is a device used to collect money in exchange for the right to park a vehicle in a particular place for a limited amount of time. Parking meters can be used by municipalities as a tool for enforcing their integrated on-street par ...
, posing as quick payment options, as seen in
Austin Austin is the capital city of the U.S. state of Texas, as well as the seat and largest city of Travis County, with portions extending into Hays and Williamson counties. Incorporated on December 27, 1839, it is the 11th-most-populous city ...
,
San Antonio ("Cradle of Freedom") , image_map = , mapsize = 220px , map_caption = Interactive map of San Antonio , subdivision_type = Country , subdivision_name = United States , subdivision_type1= U.S. state, State , subdivision_name1 = Texas , s ...
and
Boston Boston (), officially the City of Boston, is the state capital and most populous city of the Commonwealth of Massachusetts, as well as the cultural and financial center of the New England region of the United States. It is the 24th- mo ...
, among other cities across the United States and Australia.


See also

*
Aztec Code The Aztec Code is a matrix code invented by Andrew Longacre, Jr. and Robert Hussey in 1995.* The code was published by AIM, Inc. in 1997. Although the Aztec Code was patented, that patent was officially made public domain. Click "images" the ...
*
Data Matrix A Data Matrix is a two-dimensional code consisting of black and white "cells" or dots arranged in either a square or rectangular pattern, also known as a matrix. The information to be encoded can be text or numeric data. Usual data size is fro ...
*
PDF417 PDF417 is a stacked linear barcode format used in a variety of applications such as transport, identification cards, and inventory management. "PDF" stands for Portable Data File. The "417" signifies that each pattern in the code consists of 4 ...
*
QRpedia QRpedia is a mobile Web-based system which uses QR codes to deliver Wikipedia articles to users, in their preferred language. A typical use is on museum labels, linking to Wikipedia articles about the exhibited object. QR codes can easily be gene ...
* SnapTag *
SPARQCode A SPARQCode is a matrix code (or two-dimensional bar code) encoding standard that is based on the physical QR Code definition created by Japanese corporation Denso-Wave. Overview The QR Code standard as defined by Denso-Wave in ISO/IEC 180 ...
* Touchatag


References


Bibliography

* *


External links

* Reed Solomon Codes for Coders – an elaborate tutorial on Wikiversity, covering both QR code structure and the Reed Solomon codes used to encode the data. {{Authority control, state=autocollapse 1994 introductions Automatic identification and data capture Barcodes Encodings Hypermedia Japanese inventions