What is barcode symbology?

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There are many different types of barcodes, which are called symbologies. They vary by the amount and type (e.g., numeric only or alphanumeric). The most common difference between symbology types is 1-Dimensional (1D) and 2-Dimensional (2D) codes.


1D and 2D symbologies do differ and therefore support different types and amounts of data. The type of barcode that is being used in the application environment will impact the type of scanner that is needed to read it.

1D barcode symbology examples include UPC-A (Data capacity of twelve numeric digits - eleven user specified and one check digit), UPC-E (Data Capacity of seven numeric digits - six user specified and one check digit), Code 128 (Variable length alphanumeric data) and 1, 2 of 5 (Variable length numeric data).

2D barcodes store data horizontally and vertically so more data can be encoded in a much smaller space for better error correction. Examples include data matrix (Consists of any type of data including binary or alphanumeric and be up to 3116 bytes in length), aztec (Consists of any type of data including binary or alphanumeric and be up to 3750 bytes in length), maxicode (Holds up to 93 alphanumeric characters or  138 numeric digits) and QR Code (Consist of any type of data including binary or alphanumeric and be up to 7089 bytes in length).

1D symbologies encode data horizontally along with barcode and can store a limited amount of information (around 85 characters maximum but typically much less, depending on the code type). As more data is encoded, the barcode becomes wider.

2D symbologies have a two-dimensional way of representing data and can store a greater amount of information (hundreds of characters) compared to a 1D code. As more data is encoded, the size of the barcode can be increased in both the horizontal and vertical directions, thus maintaining a manageable shape for easy scanning. To properly decode the data, a scanner must read the entire symbol, in both dimensions.

Determining the best barcode symbology depends on the type and amount of data required, and the marking space available. The same symbology is not required for all items, because barcode readers can recognize and decode multiple barcode formats. There are more than 200 barcode symbologies, but only a few are appropriate for unit-dose identification. The three leading symbologies for unit-of-use labeling are Code 128, Code 39, and the reduced space symbology (RSS) family. Below are overviews of the main symbologies:

CODE 120

One of the densest linear symbologies, encodes the full 128-character ASCII character set. Code 128 is a variable-length symbology, so symbols can be as long as necessary to encode required data.


Also called code 3 of 9, it is one of the oldest and most widely used symbologies. It is a variable-length alphanumeric symbology for encoding 26 capital letters plus numerals and seven special characters. An extended version is available that supports all 128 ASCII characters. Code 39 is less dense than Code 128, thus requiring more room on the package.


The RSS family of symbologies finds use in limited-space applications. RSS-14 is an all-numeric symbology that is the leading option for unit-of-use pharmaceutical marketing, and is also used on wristbands. RSS stacked is an alphanumeric symbology providing additional data capacity by stacking a series of RSS symbols. Other symbologies in the RSS family, including RSS Truncated and RSS Composite, provide options for additional space savings and data capacity.


Although not applied by manufacturers because it is a 2D symbology, it has a legacy of use in medication administration and other healthcare applications. Laser scanners cannot read data matrix, but other types of barcode readers and label printers support the format.


A 2D symbology that resembles a series of small linear codes stacked upon each other. PDF417 offers high data capacity in a realtively small space, enabling the encoding of up to 2,000 alphanumeric characters encoded, although symbols printed for unit-dose sizes would hold considerably fewer. PDF417 is a popular option for wristbands when organizations require information beyond the patient name or ID number.


A 2D matrix symbology containing from 13 to 3,832 numeric characters or 12 to 3,067 alphabetic characters. Aztec mesas are aztec code-based supplements that enable linear barcode symbols to encode additional information. The resulting symbol is a composite of linear and 2D symbologies.