Design of generalized search interfaces for health informatics

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 one-dimensional (1D), can be scanned by special optical scanners, called barcode readers, of which there are several types.

Later, two-dimensional (2D) variants were developed, using rectangles, dots, hexagons and other patterns, called 2D barcodes or matrix codes, although they do not use bars as such. Both can be read using purpose-built 2D optical scanners, which exist in a few different forms. Matrix codes can also be read by a digital camera connected to a microcomputer running software that takes a photographic image of the barcode and analyzes the image to deconstruct and decode the code. A mobile device with a built-in camera, such as a smartphone, can function as the latter type of barcode reader using specialized application software and is suitable for both 1D and 2D codes.

The barcode was invented by Norman Joseph Woodland and Bernard Silver and patented in the US in 1952.^[1] The invention was based on Morse code^[2] that was extended to thin and thick bars. However, it took over twenty years before this invention became commercially successful. UK magazine Modern Railways December 1962 pages 387–389 record how British Railways had already perfected a barcode-reading system capable of correctly reading rolling stock travelling at 100 mph (160 km/h) with no mistakes. An early use of one type of barcode in an industrial context was sponsored by the Association of American Railroads in the late 1960s. Developed by General Telephone and Electronics (GTE) and called KarTrak ACI (Automatic Car Identification), this scheme involved placing colored stripes in various combinations on steel plates which were affixed to the sides of railroad rolling stock. Two plates were used per car, one on each side, with the arrangement of the colored stripes encoding information such as ownership, type of equipment, and identification number.^[3] The plates were read by a trackside scanner located, for instance, at the entrance to a classification yard, while the car was moving past.^[4] The project was abandoned after about ten years because the system proved unreliable after long-term use.^[3]

Barcodes became commercially successful when they were used to automate supermarket checkout systems, a task for which they have become almost universal. The Uniform Grocery Product Code Council had chosen, in 1973, the barcode design developed by George Laurer. Laurer's barcode, with vertical bars, printed better than the circular barcode developed by Woodland and Silver.^[5] Their use has spread to many other tasks that are generically referred to as automatic identification and data capture (AIDC). The first successful system using barcodes was in the UK supermarket group Sainsbury's in 1972 using shelf-mounted barcodes which were developed by Plessey.^[6][7] In June 1974, Marsh supermarket in Troy, Ohio used a scanner made by Photographic Sciences Corporation to scan the Universal Product Code (UPC) barcode on a pack of Wrigley's chewing gum.^[8][5] QR codes, a specific type of 2D barcode, rose in popularity in the second decade of the 2000s due to the growth in smartphone ownership.^[9]

Other systems have made inroads in the AIDC market, but the simplicity, universality and low cost of barcodes has limited the role of these other systems, particularly before technologies such as radio-frequency identification (RFID) became available after 2023.

In 1948, Bernard Silver, a graduate student at Drexel Institute of Technology in Philadelphia, Pennsylvania, US overheard the president of the local food chain, Food Fair, asking one of the deans to research a system to automatically read product information during checkout.^[10] Silver told his friend Norman Joseph Woodland about the request, and they started working on a variety of systems. Their first working system used ultraviolet ink, but the ink faded too easily and was expensive.^[11]

Convinced that the system was workable with further development, Woodland left Drexel, moved into his father's apartment in Florida, and continued working on the system. His next inspiration came from Morse code, and he formed his first barcode from sand on the beach. "I just extended the dots and dashes downwards and made narrow lines and wide lines out of them."^[11] To read them, he adapted technology from optical soundtracks in movies, using a 500-watt incandescent light bulb shining through the paper onto an RCA935 photomultiplier tube (from a movie projector) on the far side. He later decided that the system would work better if it were printed as a circle instead of a line, allowing it to be scanned in any direction.

On 20 October 1949 Woodland and Silver filed a patent application for "Classifying Apparatus and Method", in which they described both the linear and bull's eye printing patterns, as well as the mechanical and electronic systems needed to read the code. The patent was issued on 7 October 1952 as US Patent 2,612,994.^[1] In 1951, Woodland moved to IBM and continually tried to interest IBM in developing the system. The company eventually commissioned a report on the idea, which concluded that it was both feasible and interesting, but that processing the resulting information would require equipment that was some time off in the future.

IBM offered to buy the patent, but the offer was not accepted. Philco purchased the patent in 1962 and then sold it to RCA sometime later.^[11]

During his time as an undergraduate, David Jarrett Collins worked at the Pennsylvania Railroad and became aware of the need to automatically identify railroad cars. Immediately after receiving his master's degree from MIT in 1959, he started work at GTE Sylvania and began addressing the problem. He developed a system called KarTrak using blue, white and red reflective stripes attached to the side of the cars, encoding a four-digit company identifier and a six-digit car number.^[11] Light reflected off the colored stripes was read by photomultiplier vacuum tubes.^[12]

The Boston and Maine Railroad tested the KarTrak system on their gravel cars in 1961. The tests continued until 1967, when the Association of American Railroads (AAR) selected it as a standard, automatic car identification, across the entire North American fleet. The installations began on 10 October 1967. However, the economic downturn and rash of bankruptcies in the industry in the early 1970s greatly slowed the rollout, and it was not until 1974 that 95% of the fleet was labeled. To add to its woes, the system was found to be easily fooled by dirt in certain applications, which greatly affected accuracy. The AAR abandoned the system in the late 1970s, and it was not until the mid-1980s that they introduced a similar system, this time based on radio tags.^[13]

The railway project had failed, but a toll bridge in New Jersey requested a similar system so that it could quickly scan for cars that had purchased a monthly pass. Then the US Post Office requested a system to track trucks entering and leaving their facilities. These applications required special retroreflector labels. Finally, Kal Kan asked the Sylvania team for a simpler (and cheaper) version which they could put on cases of pet food for inventory control.

In 1967, with the railway system maturing, Collins went to management looking for funding for a project to develop a black-and-white version of the code for other industries. They declined, saying that the railway project was large enough, and they saw no need to branch out so quickly.

Collins then quit Sylvania and formed the Computer Identics Corporation.^[11] As its first innovations, Computer Identics moved from using incandescent light bulbs in its systems, replacing them with helium–neon lasers, and incorporated a mirror as well, making it capable of locating a barcode up to a meter (3 feet) in front of the scanner. This made the entire process much simpler and more reliable, and typically enabled these devices to deal with damaged labels, as well, by recognizing and reading the intact portions.

Computer Identics Corporation installed one of its first two scanning systems in the spring of 1969 at a General Motors (Buick) factory in Flint, Michigan.^[11] The system was used to identify a dozen types of transmissions moving on an overhead conveyor from production to shipping. The other scanning system was installed at General Trading Company's distribution center in Carlstadt, New Jersey to direct shipments to the proper loading bay.

In 1966 the National Association of Food Chains (NAFC) held a meeting on the idea of automated checkout systems. RCA, which had purchased the rights to the original Woodland patent, attended the meeting and initiated an internal project to develop a system based on the bullseye code. The Kroger grocery chain volunteered to test it.

In the mid-1970s the NAFC established the Ad-Hoc Committee for U.S. Supermarkets on a Uniform Grocery-Product Code to set guidelines for barcode development. In addition, it created a symbol-selection subcommittee to help standardize the approach. In cooperation with consulting firm, McKinsey & Co., they developed a standardized 11-digit code for identifying products. The committee then sent out a contract tender to develop a barcode system to print and read the code. The request went to Singer, National Cash Register (NCR), Litton Industries, RCA, Pitney-Bowes, IBM and many others.^[14] A wide variety of barcode approaches was studied, including linear codes, RCA's bullseye concentric circle code, starburst patterns and others.

In the spring of 1971 RCA demonstrated their bullseye code at another industry meeting. IBM executives at the meeting noticed the crowds at the RCA booth and immediately developed their own system. IBM marketing specialist Alec Jablonover remembered that the company still employed Woodland, and he established a new facility in Research Triangle Park to lead development.

In July 1972 RCA began an 18-month test in a Kroger store in Cincinnati. Barcodes were printed on small pieces of adhesive paper, and attached by hand by store employees when they were adding price tags. The code proved to have a serious problem; the printers would sometimes smear ink, rendering the code unreadable in most orientations. However, a linear code, like the one being developed by Woodland at IBM, was printed in the direction of the stripes, so extra ink would simply make the code "taller" while remaining readable. So on 3 April 1973 the IBM UPC was selected as the NAFC standard. IBM had designed five versions of UPC symbology for future industry requirements: UPC A, B, C, D, and E.^[15]

NCR installed a testbed system at Marsh's Supermarket in Troy, Ohio, near the factory that was producing the equipment. On 26 June 1974, a 10-pack of Wrigley's Juicy Fruit gum was scanned, registering the first commercial use of the UPC.^[16]

In 1971 an IBM team was assembled for an intensive planning session, threshing out, 12 to 18 hours a day, how the technology would be deployed and operate cohesively across the system, and scheduling a roll-out plan. By 1973, the team were meeting with grocery manufacturers to introduce the symbol that would need to be printed on the packaging or labels of all of their products. There were no cost savings for a grocery to use it, unless at least 70% of the grocery's products had the barcode printed on the product by the manufacturer. IBM projected that 75% would be needed in 1975.

Economic studies conducted for the grocery industry committee projected over $40 million in savings to the industry from scanning by the mid-1970s. Those numbers were not achieved in that time-frame and some predicted the demise of barcode scanning. The usefulness of the barcode required the adoption of expensive scanners by a critical mass of retailers while manufacturers simultaneously adopted barcode labels. Neither wanted to move first and results were not promising for the first couple of years, with Business Week proclaiming "The Supermarket Scanner That Failed" in a 1976 article.^[16][17]

Sims Supermarkets were the first location in Australia to use barcodes, starting in 1979.^[18]

A barcode system is a network of hardware and software, consisting primarily of mobile computers, printers, handheld scanners, infrastructure, and supporting software. Barcode systems are used to automate data collection where hand recording is neither timely nor cost effective. Despite often being provided by the same company, Barcoding systems are not radio-frequency identification (RFID) systems. Many companies use both technologies as part of larger resource management systems.

A typical barcode system consist of some infrastructure, either wired or wireless that connects some number of mobile computers, handheld scanners, and printers to one or many databases that store and analyze the data collected by the system. At some level there must be some software to manage the system. The software may be as simple as code that manages the connection between the hardware and the database or as complex as an ERP, MRP, or some other inventory management software.

A wide range of hardware is manufactured for use in barcode systems by such manufacturers as Datalogic, Intermec, HHP (Hand Held Products), Microscan Systems, Unitech, Metrologic, PSC, and PANMOBIL, with the best known brand of handheld scanners and mobile computers being produced by Symbol,^{[citation needed]} a division of Motorola.

Some ERP, MRP, and other inventory management software have built in support for barcode reading. Alternatively, custom interfaces can be created using a language such as C++, C#, Java, Visual Basic.NET, and many others. In addition, software development kits are produced to aid the process.

In 1981 the United States Department of Defense adopted the use of Code 39 for marking all products sold to the United States military. This system, Logistics Applications of Automated Marking and Reading Symbols (LOGMARS), is still used by DoD and is widely viewed as the catalyst for widespread adoption of barcoding in industrial uses.^[19]

Barcodes are widely used around the world in many contexts. In stores, UPC barcodes are pre-printed on most items other than fresh produce from a grocery store. This speeds up processing at check-outs and helps track items and also reduces instances of shoplifting involving price tag swapping, although shoplifters can now print their own barcodes.^[20] Barcodes that encode a book's ISBN are also widely pre-printed on books, journals and other printed materials. In addition, retail chain membership cards use barcodes to identify customers, allowing for customized marketing and greater understanding of individual consumer shopping patterns. At the point of sale, shoppers can get product discounts or special marketing offers through the address or e-mail address provided at registration.

Barcodes are widely used in healthcare and hospital settings, ranging from patient identification (to access patient data, including medical history, drug allergies, etc.) to creating SOAP notes^[21] with barcodes to medication management. They are also used to facilitate the separation and indexing of documents that have been imaged in batch scanning applications, track the organization of species in biology,^[22] and integrate with in-motion checkweighers to identify the item being weighed in a conveyor line for data collection.

They can also be used to keep track of objects and people; they are used to keep track of rental cars, airline luggage, nuclear waste, express mail, and parcels. Barcoded tickets (which may be printed by the customer on their home printer, or stored on their mobile device) allow the holder to enter sports arenas, cinemas, theatres, fairgrounds, and transportation, and are used to record the arrival and departure of vehicles from rental facilities etc. This can allow proprietors to identify duplicate or fraudulent tickets more easily. Barcodes are widely used in shop floor control applications software where employees can scan work orders and track the time spent on a job.

Barcodes are also used in some kinds of non-contact 1D and 2D position sensors. A series of barcodes are used in some kinds of absolute 1D linear encoder. The barcodes are packed close enough together that the reader always has one or two barcodes in its field of view. As a kind of fiducial marker, the relative position of the barcode in the field of view of the reader gives incremental precise positioning, in some cases with sub-pixel resolution. The data decoded from the barcode gives the absolute coarse position. An "address carpet", used in digital paper, such as Howell's binary pattern and the Anoto dot pattern, is a 2D barcode designed so that a reader, even though only a tiny portion of the complete carpet is in the field of view of the reader, can find its absolute X, Y position and rotation in the carpet.^[23][24]

Matrix codes can embed a hyperlink to a web page. A mobile device with a built-in camera might be used to read the pattern and browse the linked website, which can help a shopper find the best price for an item in the vicinity. Since 2005, airlines use an IATA-standard 2D barcode on boarding passes (Bar Coded Boarding Pass (BCBP)), and since 2008 2D barcodes sent to mobile phones enable electronic boarding passes.^[25]

Some applications for barcodes have fallen out of use. In the 1970s and 1980s, software source code was occasionally encoded in a barcode and printed on paper (Cauzin Softstrip and Paperbyte^[26] are barcode symbologies specifically designed for this application), and the 1991 Barcode Battler computer game system used any standard barcode to generate combat statistics.

Artists have used barcodes in art, such as Scott Blake's Barcode Jesus, as part of the post-modernism movement.

The mapping between messages and barcodes is called a symbology. The specification of a symbology includes the encoding of the message into bars and spaces, any required start and stop markers, the size of the quiet zone required to be before and after the barcode, and the computation of a checksum.

Linear symbologies can be classified mainly by two properties:

Continuous vs. discrete

• Characters in discrete symbologies are composed of n bars and n − 1 spaces. There is an additional space between characters, but it does not convey information, and may have any width as long as it is not confused with the end of the code.
• Characters in continuous symbologies are composed of n bars and n spaces, and usually abut, with one character ending with a space and the next beginning with a bar, or vice versa. A special end pattern that has bars on both ends is required to end the code.

Two-width vs. many-width

• A two-width, also called a binary bar code, contains bars and spaces of two widths, "wide" and "narrow". The precise width of the wide bars and spaces is not critical; typically, it is permitted to be anywhere between 2 and 3 times the width of the narrow equivalents.
• Some other symbologies use bars of two different heights (POSTNET), or the presence or absence of bars (CPC Binary Barcode). These are normally also considered binary bar codes.
• Bars and spaces in many-width symbologies are all multiples of a basic width called the module; most such codes use four widths of 1, 2, 3 and 4 modules.

Some symbologies use interleaving. The first character is encoded using black bars of varying width. The second character is then encoded by varying the width of the white spaces between these bars. Thus, characters are encoded in pairs over the same section of the barcode. Interleaved 2 of 5 is an example of this.

Stacked symbologies repeat a given linear symbology vertically.

The most common among the many 2D symbologies are matrix codes, which feature square or dot-shaped modules arranged on a grid pattern. 2D symbologies also come in circular and other patterns and may employ steganography, hiding modules within an image (for example, DataGlyphs).

Linear symbologies are optimized for laser scanners, which sweep a light beam across the barcode in a straight line, reading a slice of the barcode light-dark patterns. Scanning at an angle makes the modules appear wider, but does not change the width ratios. Stacked symbologies are also optimized for laser scanning, with the laser making multiple passes across the barcode.

In the 1990s development of charge-coupled device (CCD) imagers to read barcodes was pioneered by Welch Allyn. Imaging does not require moving parts, as a laser scanner does. In 2007, linear imaging had begun to supplant laser scanning as the preferred scan engine for its performance and durability.

2D symbologies cannot be read by a laser, as there is typically no sweep pattern that can encompass the entire symbol. They must be scanned by an image-based scanner employing a CCD or other digital camera sensor technology.

The earliest, and still^[when?] the cheapest, barcode scanners are built from a fixed light and a single photosensor that is manually moved across the barcode. Barcode scanners can be classified into three categories based on their connection to the computer. The older type is the RS-232 barcode scanner. This type requires special programming for transferring the input data to the application program. Keyboard interface scanners connect to a computer using a PS/2 or AT keyboard–compatible adaptor cable (a "keyboard wedge"). The barcode's data is sent to the computer as if it had been typed on the keyboard.

Like the keyboard interface scanner, USB scanners do not need custom code for transferring input data to the application program. On PCs running Windows the human interface device emulates the data merging action of a hardware "keyboard wedge", and the scanner automatically behaves like an additional keyboard.

Most modern smartphones are able to decode barcode using their built-in camera. Google's mobile Android operating system can use their own Google Lens application to scan QR codes, or third-party apps like Barcode Scanner to read both one-dimensional barcodes and QR codes. Google's Pixel devices can natively read QR codes inside the default Pixel Camera app. Nokia's Symbian operating system featured a barcode scanner,^[27] while mbarcode^[28] is a QR code reader for the Maemo operating system. In Apple iOS 11, the native camera app can decode QR codes and can link to URLs, join wireless networks, or perform other operations depending on the QR Code contents.^[29] Other paid and free apps are available with scanning capabilities for other symbologies or for earlier iOS versions.^[30] With BlackBerry devices, the App World application can natively scan barcodes and load any recognized Web URLs on the device's Web browser. Windows Phone 7.5 is able to scan barcodes through the Bing search app. However, these devices are not designed specifically for the capturing of barcodes. As a result, they do not decode nearly as quickly or accurately as a dedicated barcode scanner or portable data terminal.^{[citation needed]}

It is common for producers and users of bar codes to have a quality management system which includes verification and validation of bar codes.^[31] Barcode verification examines scanability and the quality of the barcode in comparison to industry standards and specifications.^[32] Barcode verifiers are primarily used by businesses that print and use barcodes. Any trading partner in the supply chain can test barcode quality. It is important to verify a barcode to ensure that any reader in the supply chain can successfully interpret a barcode with a low error rate. Retailers levy large penalties for non-compliant barcodes. These chargebacks can reduce a manufacturer's revenue by 2% to 10%.^[33]

A barcode verifier works the way a reader does, but instead of simply decoding a barcode, a verifier performs a series of tests. For linear barcodes these tests are:

• Edge contrast (EC)^[34]
  • The difference between the space reflectance (Rs) and adjoining bar reflectance (Rb). EC=Rs-Rb
• Minimum bar reflectance (Rb)^[34]
  • The smallest reflectance value in a bar.
• Minimum space reflectance (Rs)^[34]
  • The smallest reflectance value in a space.
• Symbol contrast (SC)^[34]
  • Symbol contrast is the difference in reflectance values of the lightest space (including the quiet zone) and the darkest bar of the symbol. The greater the difference, the higher the grade. The parameter is graded as either A, B, C, D, or F. SC=Rmax-Rmin
• Minimum edge contrast (ECmin)^[34]
  • The difference between the space reflectance (Rs) and adjoining bar reflectance (Rb). EC=Rs-Rb
• Modulation (MOD)^[34]
  • The parameter is graded either A, B, C, D, or F. This grade is based on the relationship between minimum edge contrast (ECmin) and symbol contrast (SC). MOD=ECmin/SC The greater the difference between minimum edge contrast and symbol contrast, the lower the grade. Scanners and verifiers perceive the narrower bars and spaces to have less intensity than wider bars and spaces; the comparison of the lesser intensity of narrow elements to the wide elements is called modulation. This condition is affected by aperture size.
• Inter-character gap^[34]
  • In discrete barcodes, the space that disconnects the two contiguous characters. When present, inter-character gaps are considered spaces (elements) for purposes of edge determination and reflectance parameter grades.
• Defects
• Decode^[34]
  • Extracting the information which has been encoded in a bar code symbol.
• Decodability^[34]
  • Can be graded as A, B, C, D, or F. The Decodability grade indicates the amount of error in the width of the most deviant element in the symbol. The less deviation in the symbology, the higher the grade. Decodability is a measure of print accuracy using the symbology reference decode algorithm.

2D matrix symbols look at the parameters:

• Symbol contrast^[34]
• Modulation^[34]
• Decode^[34]
• Unused error correction
• Fixed (finder) pattern damage
• Grid non-uniformity
• Axial non-uniformity^[35]

Depending on the parameter, each ANSI test is graded from 0.0 to 4.0 (F to A), or given a pass or fail mark. Each grade is determined by analyzing the scan reflectance profile (SRP), an analog graph of a single scan line across the entire symbol. The lowest of the 8 grades is the scan grade, and the overall ISO symbol grade is the average of the individual scan grades. For most applications a 2.5 (C) is the minimal acceptable symbol grade.^[36]

Compared with a reader, a verifier measures a barcode's optical characteristics to international and industry standards. The measurement must be repeatable and consistent. Doing so requires constant conditions such as distance, illumination angle, sensor angle and verifier aperture. Based on the verification results, the production process can be adjusted to print higher quality barcodes that will scan down the supply chain.

Bar code validation may include evaluations after use (and abuse) testing such as sunlight, abrasion, impact, moisture, etc.^[37]

Barcode verifier standards are defined by the International Organization for Standardization (ISO), in ISO/IEC 15426-1 (linear) or ISO/IEC 15426-2 (2D).^{[citation needed]} The current international barcode quality specification is ISO/IEC 15416 (linear) and ISO/IEC 15415 (2D).^{[citation needed]} The European Standard EN 1635 has been withdrawn and replaced by ISO/IEC 15416. The original U.S. barcode quality specification was ANSI X3.182. (UPCs used in the US – ANSI/UCC5).^{[citation needed]} As of 2011 the ISO workgroup JTC1 SC31 was developing a Direct Part Marking (DPM) quality standard: ISO/IEC TR 29158.^[38]

In point-of-sale management, barcode systems can provide detailed up-to-date information on the business, accelerating decisions and with more confidence. For example:

• Fast-selling items can be identified quickly and automatically reordered.
• Slow-selling items can be identified, preventing inventory build-up.
• The effects of merchandising changes can be monitored, allowing fast-moving, more profitable items to occupy the best space.
• Historical data can be used to predict seasonal fluctuations very accurately.
• Items may be repriced on the shelf to reflect both sale prices and price increases.
• This technology also enables the profiling of individual consumers, typically through a voluntary registration of discount cards. While pitched as a benefit to the consumer, this practice is considered to be potentially dangerous by privacy advocates.^[which?]

Besides sales and inventory tracking, barcodes are very useful in logistics and supply chain management.

• When a manufacturer packs a box for shipment, a unique identifying number (UID) can be assigned to the box.
• A database can link the UID to relevant information about the box; such as order number, items packed, quantity packed, destination, etc.
• The information can be transmitted through a communication system such as electronic data interchange (EDI) so the retailer has the information about a shipment before it arrives.
• Shipments that are sent to a distribution center (DC) are tracked before forwarding. When the shipment reaches its final destination, the UID gets scanned, so the store knows the shipment's source, contents, and cost.

Barcode scanners are relatively low cost and extremely accurate compared to key-entry, with only about 1 substitution error in 15,000 to 36 trillion characters entered.^{[39][unreliable source?]} The exact error rate depends on the type of barcode.

A first generation, "one dimensional" barcode that is made up of lines and spaces of various widths or sizes that create specific patterns.

Example	Symbology	Continuous or discrete	Bar type	Uses
	Codabar	Discrete	Two	Old format used in libraries and blood banks and on airbills (out of date, but still widely used in libraries)
	Code 25 – Non-interleaved 2 of 5	Continuous	Two	Industrial
	Code 25 – Interleaved 2 of 5	Continuous	Two	Wholesale, libraries International standard ISO/IEC 16390
	Code 11	Discrete	Two	Telephones (out of date)
	Farmacode or Code 32	Discrete	Two	Italian pharmacode – use Code 39 (no international standard available)
	Code 39	Discrete	Two	Various – international standard ISO/IEC 16388
	Code 93	Continuous	Many	Various
	Code 128	Continuous	Many	Various – International Standard ISO/IEC 15417
	CPC Binary	Discrete	Two
	Data Logic 2 of 5	Discrete	Two	Datalogic 2 of 5 can encode digits 0–9 and was used mostly in Chinese Postal Services.
	EAN 2	Continuous	Many	Addon code (magazines), GS1-approved – not an own symbology – to be used only with an EAN/UPC according to ISO/IEC 15420
	EAN 5	Continuous	Many	Addon code (books), GS1-approved – not an own symbology – to be used only with an EAN/UPC according to ISO/IEC 15420
	EAN-8, EAN-13	Continuous	Many	Worldwide retail, GS1-approved – International Standard ISO/IEC 15420
||  |  ||	Facing Identification Mark	Discrete	Two	USPS business reply mail
	GS1-128 (formerly named UCC/EAN-128), incorrectly referenced as EAN 128 and UCC 128	Continuous	Many	Various, GS1-approved – just an application of the Code 128 (ISO/IEC 15417) using the ANS MH10.8.2 AI Datastructures. It is not a separate symbology.
	GS1 DataBar, formerly Reduced Space Symbology (RSS)	Continuous	Many	Various, GS1-approved
	IATA 2 of 5	Discrete	Two	IATA 2 of 5 version of Industrial 2 of 5 is used by International Air Transport Association had fixed 17 digits length with 16 valuable package identification digit and 17-th check digit.
	Industrial 2 of 5	Discrete	Two	Industrial 2 of 5 can encode only digits 0–9 and at this time has only historical value.
	ITF-14	Continuous	Two	Non-retail packaging levels, GS1-approved – is just an Interleaved 2/5 Code (ISO/IEC 16390) with a few additional specifications, according to the GS1 General Specifications
	ITF-6	Continuous	Two	Interleaved 2 of 5 barcode to encode an addon to ITF-14 and ITF-16 barcodes. The code is used to encode additional data such as items quantity or container weight
	JAN	Continuous	Many	Used in Japan, similar to and compatible with EAN-13 (ISO/IEC 15420)
	Japan Post barcode	Discrete	4 bar heights	Japan Post
	Matrix 2 of 5	Discrete	Two	Matrix 2 of 5 can encode digits 0–9 and was uses for warehouse sorting, photo finishing, and airline ticket marking.
	MSI	Continuous	Two	Used for warehouse shelves and inventory
	Pharmacode	Discrete	Two	Pharmaceutical packaging (no international standard available)
	PLANET	Continuous	Tall/short	United States Postal Service (no international standard available)
	Plessey	Continuous	Two	Catalogs, store shelves, inventory (no international standard available)
	Telepen	Continuous	Two	Libraries (UK)
	Universal Product Code (UPC-A and UPC-E)	Continuous	Many	Worldwide retail, GS1-approved – International Standard ISO/IEC 15420

2D barcodes consist of bars, but use both dimensions for encoding.

Example	Symbology	Continuous or discrete	Bar type	Uses
	Australia Post barcode	Discrete	4 bar heights	An Australia Post 4-state barcode as used on a business reply paid envelope and applied by automated sorting machines to other mail when initially processed in fluorescent ink.[40]
	Codablock	Continuous	Many	Codablock is a family of stacked 1D barcodes (in some cases counted as stacked 2D barcodes) which are used in health care industry (HIBC).
	Code 49	Continuous	Many	Various
	Code 16K			The Code 16K (1988) is a multi-row bar code developed by Ted Williams at Laserlight Systems (USA) in 1992. In the US and France, the code is used in the electronics industry to identify chips and printed circuit boards. Medical applications in the USA are well known. Williams also developed Code 128, and the structure of 16K is based on Code 128. Not coincidentally, 128 squared happened to equal 16,384 or 16K for short. Code 16K resolved an inherent problem with Code 49. Code 49's structure requires a large amount of memory for encoding and decoding tables and algorithms. 16K is a stacked symbology.[41][42]
	DX film edge barcode	Neither	Tall/short	Color print film
	Intelligent Mail barcode	Discrete	4 bar heights	United States Postal Service, replaces both POSTNET and PLANET symbols (formerly named OneCode)
	KarTrak ACI	Discrete	Coloured bars	Used in North America on railroad rolling equipment
	PostBar	Discrete	4 bar heights	Canadian Post office
	POSTNET	Discrete	Tall/short	United States Postal Service (no international standard available)
	RM4SCC / KIX	Discrete	4 bar heights	Royal Mail / PostNL
	RM Mailmark C	Discrete	4 bar heights	Royal Mail
	RM Mailmark L	Discrete	4 bar heights	Royal Mail
	Spotify codes	Discrete	23 bar heights	Spotify codes point to artists, songs, podcasts, playlists, and albums. The information is encoded in the height of the bars;[43] so as long as the bar heights are maintained, the code can be handwritten and can vary in color.[44] Patented under EP3444755.

A matrix code or simply a 2D code, is a two-dimensional way to represent information. It can represent more data per unit area. Apart from dots various other patterns can be used.

Example	Name	Notes
	App Clip Code	Apple-proprietary code for launching "App Clips", a type of applet. 5 concentric rings of three colors (light, dark, middle).[45]
aruco code	aruco code	https://docs.opencv.org/4.x/d5/dae/tutorial_aruco_detection.html
	AR Code	A type of marker used for placing content inside augmented reality applications. Some AR Codes can contain QR codes inside, so that AR content can be linked to.[46] See also ARTag.
	Aztec Code	Designed by Andrew Longacre at Welch Allyn (now Honeywell Scanning and Mobility). Public domain. – International Standard: ISO/IEC 24778
	bCode	A matrix designed for the study of insect behavior.[47] Encodes an 11 bit identifier and 16 bits of read error detection and error correction information. Predominantly used for marking honey bees, but can also be applied to other animals.
	BEEtag	A 25 bit (5x5) code matrix of black and white pixels that is unique to each tag surrounded by a white pixel border and a black pixel border. The 25-bit matrix consists of a 15-bit identity code, and a 10-bit error check.[48] It is designed to be a low-cost, image-based tracking system for the study of animal behavior and locomotion.
	BeeTagg	A 2D code with honeycomb structures suitable for mobile tagging and was developed by the Swiss company connvision AG.
	Bokode	A type of data tag which holds much more information than a barcode over the same area. They were developed by a team led by Ramesh Raskar at the MIT Media Lab. The bokode pattern is a tiled series of Data Matrix codes.
	Boxing	A high-capacity 2D code is used on piqlFilm by Piql AS[49]
	Cauzin Softstrip	Softstrip code was used in the 1980s to encode software, which could be transferred by special scanners from printed journals into computer hardware.
	Code 1	Public domain. Code 1 is currently used in the health care industry for medicine labels and the recycling industry to encode container content for sorting.[50]
	ColorCode	ColorZip[51] developed colour barcodes that can be read by camera phones from TV screens; mainly used in Korea.[52]
	Color Construct Code	Color Construct Code is one of the few code symbologies designed to take advantage of multiple colors.[53][54]
	Cronto Visual Cryptogram	The Cronto Visual Cryptogram (also called photoTAN) is a specialized color barcode, spun out from research at the University of Cambridge by Igor Drokov, Steven Murdoch, and Elena Punskaya.[55] It is used for transaction signing in e-banking; the barcode contains encrypted transaction data which is then used as a challenge to compute a transaction authentication number using a security token.[56]
	CyberCode	From Sony.
	d-touch	readable when printed on deformable gloves and stretched and distorted[57][58]
	DataGlyphs	From Palo Alto Research Center (also termed Xerox PARC).[59] Patented.[60] DataGlyphs can be embedded into a half-tone image or background shading pattern in a way that is almost perceptually invisible, similar to steganography.[61][62]
	Data Matrix	From Microscan Systems, formerly RVSI Acuity CiMatrix/Siemens. Public domain. Increasingly used throughout the United States. Single segment Data Matrix is also termed Semacode. – International Standard: ISO/IEC 16022.
	Datastrip Code	From Datastrip, Inc.
	Digimarc code	The Digimarc Code is a unique identifier, or code, based on imperceptible patterns that can be applied to marketing materials, including packaging, displays, ads in magazines, circulars, radio and television[63]
	digital paper	patterned paper used in conjunction with a digital pen to create handwritten digital documents. The printed dot pattern uniquely identifies the position coordinates on the paper.
	Dolby Digital	Digital sound code for printing on cinematic film between the threading holes
	DotCode	Standardized as ISS DotCode Symbology Specification 4.0. Public domain. Extended 2D replacement of Code 128 barcode. At this time is used to track individual cigarette and pharmaceutical packages.
	Dot Code A	Also known as Philips Dot Code.[64] Patented in 1988.[65]
	DWCode	Introduced by GS1 US and GS1 Germany, the DWCode is a unique, imperceptible data carrier that is repeated across the entire graphics design of a package[66]
	EZcode	Designed for decoding by cameraphones;[67] from ScanLife.[68]
	Han Xin code	Code designed to encode Chinese characters, invented in 2007 by Chinese company The Article Numbering Center of China, introduced by Association for Automatic Identification and Mobility in 2011 and published as ISO/IEC 20830:2021 in 2021.
	High Capacity Color Barcode	HCCB was developed by Microsoft; licensed by ISAN-IA.
	HueCode	From Robot Design Associates. Uses greyscale or colour.[69]
	InterCode	From Iconlab, Inc. The standard 2D Code in South Korea. All 3 South Korean mobile carriers put the scanner program of this code into their handsets to access mobile internet, as a default embedded program.
	JAB Code	Just Another Bar Code is a colored 2D Code. Square or rectangle. License free
	MaxiCode	Used by United Parcel Service. Now public domain.
	mCode	Designed by NextCode Corporation, specifically to work with mobile phones and mobile services.[70] It is implementing an independent error detection technique preventing false decoding, it uses a variable-size error correction polynomial, which depends on the exact size of the code.[71]
	Messenger Codes	Proprietary ring-shaped code for Facebook Messenger. Defunct as of 2019, replaced by standard QR codes.
	Micro QR code	Micro QR code is a smaller version of the QR code standard for applications where symbol size is limited.
	Micro PDF417	MicroPDF417 is a restricted size barcode, similar to PDF417, which is used to add additional data to linear barcodes.
	MMCC	Designed to disseminate high capacity mobile phone content via existing colour print and electronic media, without the need for network connectivity
	NexCode	NexCode is developed and patented by S5 Systems.
	Nintendo Dot code	Developed by Olympus Corporation to store songs, images, and mini-games for Game Boy Advance on Pokémon trading cards.
	PDF417	Originated by Symbol Technologies. Public domain. – International standard: ISO/IEC 15438
	Ocode	A proprietary matrix code in hexagonal shape.[72]
	Qode	American proprietary and patented 2D Code from NeoMedia Technologies, Inc.[68]
	QR code	Initially developed, patented and owned by Denso Wave for automotive components management; they have chosen not to exercise their patent rights. Can encode Latin and Japanese Kanji and Kana characters, music, images, URLs, emails. De facto standard for Japanese cell phones. Used with BlackBerry Messenger to pick up contacts rather than using a PIN code. The most frequently used type of code to scan with smartphones, and one of the most widely used 2D Codes.[73] Public domain. – International standard: ISO/IEC 18004
	Rectangular Micro QR Code (rMQR Code)	Rectangular extension of QR Code Originated by Denso Wave . Public domain. – International standard: ISO/IEC 23941
	Screencode	Developed and patented[74][75] by Hewlett-Packard Labs. A time-varying 2D pattern using to encode data via brightness fluctuations in an image, for the purpose of high bandwidth data transfer from computer displays to smartphones via smartphone camera input. Inventors Timothy Kindberg and John Collomosse, publicly disclosed at ACM HotMobile 2008.[76]
	ShotCode	Circular pattern codes for camera phones. Originally from High Energy Magic Ltd in name Spotcode. Before that most likely termed TRIPCode.
	Snapcode, also called Boo-R code	Used by Snapchat, Spectacles, etc. US9111164B1[77][78][79]
	Snowflake Code	A proprietary code developed by Electronic Automation Ltd. in 1981. It is possible to encode more than 100 numeric digits in a space of only 5mm x 5mm. User selectable error correction allows up to 40% of the code to be destroyed and still remain readable. The code is used in the pharmaceutical industry and has an advantage that it can be applied to products and materials in a wide variety of ways, including printed labels, ink-jet printing, laser-etching, indenting or hole punching.[41][80][81]
	SPARQCode	QR code encoding standard from MSKYNET, Inc.
	TLC39	This is a combination of the two barcodes Code 39 and MicroPDF417, forming a 2D pattern. It is also known as Telecommunications Industry Forum (TCIF) Code 39 or TCIF Linked Code 39.[82]
	Trillcode	Designed for mobile phone scanning.[83] Developed by Lark Computer, a Romanian company.[71]
	VOICEYE	Developed and patented by VOICEYE, Inc. in South Korea, it aims to allow blind and visually impaired people to access printed information. It also claims to be the 2D Code that has the world's largest storage capacity.
	WeChat Mini Program code	A circular code with outward-projecting lines.[84]

• First, second and third generation barcodes
• 
  GTIN-12 number encoded in UPC-A barcode symbol. First and last digit are always placed outside the symbol to indicate Quiet Zones that are necessary for barcode scanners to work properly
• 
  EAN-13 (GTIN-13) number encoded in EAN-13 barcode symbol. First digit is always placed outside the symbol, additionally right quiet zone indicator (>) is used to indicate Quiet Zones that are necessary for barcode scanners to work properly
• 
  "Wikipedia" encoded in Code 93
• 
  "*WIKI39*" encoded in Code 39
• 
  'Wikipedia" encoded in Code 128
• 
  An example of a stacked barcode. Specifically a "Codablock" barcode.
• 
  PDF417 sample
• 
  Lorem ipsum boilerplate text as four segment Data Matrix 2D
• 
  "This is an example Aztec symbol for Wikipedia" encoded in Aztec Code
• 
  Text 'EZcode'
• 
  High Capacity Color Barcode of the URL for Wikipedia's article on High Capacity Color Barcode
• 
  "Wikipedia, The Free Encyclopedia" in several languages encoded in DataGlyphs
• 
  Two different 2D barcodes used in film: Dolby Digital between the sprocket holes with the "Double-D" logo in the middle, and Sony Dynamic Digital Sound in the blue area to the left of the sprocket holes
• 
  The QR Code for the Wikipedia URL. "Quick Response", the most popular 2D barcode. It is open in that the specification is disclosed and the patent is not exercised.^[85]
• 
  MaxiCode example. This encodes the string "Wikipedia, The Free Encyclopedia"
• 
  ShotCode sample
• 
  detail of Twibright Optar scan from laser printed paper, carrying 32 kbit/s Ogg Vorbis digital music (48 seconds per A4 page)
• 
  A KarTrak railroad Automatic Equipment Identification label on a caboose in Florida

In architecture, a building in Lingang New City by German architects Gerkan, Marg and Partners incorporates a barcode design,^[86] as does a shopping mall called Shtrikh-kod (Russian for barcode) in Narodnaya ulitsa ("People's Street") in the Nevskiy district of St. Petersburg, Russia.^[87]

In media, in 2011, the National Film Board of Canada and ARTE France launched a web documentary entitled Barcode.tv, which allows users to view films about everyday objects by scanning the product's barcode with their iPhone camera.^[88][89]

In professional wrestling, the WWE stable D-Generation X incorporated a barcode into their entrance video, as well as on a T-shirt.^[90][91]

In video games, the protagonist of the Hitman video game series has a barcode tattoo on the back of his head; QR codes can also be scanned in a side mission in Watch Dogs. The 2018 videogame Judgment features QR Codes that protagonist Takayuki Yagami can photograph with his phone camera. These are mostly to unlock parts for Yagami's Drone.^[92]

Interactive Textbooks were first published by Harcourt College Publishers to Expand Education Technology with Interactive Textbooks.^[93]

Some companies integrate custom designs into barcodes on their consumer products without impairing their readability.

Some have regarded barcodes to be an intrusive surveillance technology. Some Christians, pioneered by a 1982 book The New Money System 666 by Mary Stewart Relfe, believe the codes hide the number 666, representing the "Number of the beast".^[94] Old Believers, a separation of the Russian Orthodox Church, believe barcodes are the stamp of the Antichrist.^[95] Television host Phil Donahue described barcodes as a "corporate plot against consumers".^[96]

• Free Online Barcode Generator.