What Is the 26-Bit Wiegand Format, and How Does it Work?

Card readers and other components of access control systems need to speak a common language to function and work properly. Like most other forms of technology, access control systems use a binary number system to communicate. One of the most common formats for access systems is the 26-bit Wiegand format. It was first developed over 50 years ago, and because it’s so simple and accessible, it’s still used today. 

What is the 26 bit Wiegand format, how does it work, and where is it used? Learn more below. 

wiegand protocol explained
wiegand protocol explained

What is 26-Bit Wiegand Format? 

The 26-bit Wiegand format is a format for binary encoded data used mainly on access control devices. It’s an extremely common open format, and most access control systems are automatically designed to be able to read 26-bit Wiegand. Because it’s an open format, anybody can buy and use cards in this format, and it is possible for duplicate cards to exist. 

Although various companies make access control systems, one of the most popular brands is HID. The brand is so popular that people often refer to any access control system as an HID system. However, various brands and manufacturers make 26-bit Wiegand format access cards, not just HID. If you buy or use any basic access system, it’s highly likely that the system runs using the 26-bit Wiegand format.

This format is an industry standard known as H10301. The term “bit” refers to the numbers in the code, so each code consists of 26 numbers. Wiegand refers to the Wiegand protocol, which is the name for the wiring standard. It’s named after John R. Wiegand, whose discoveries in the 1970s laid the basis for the standard 26 bit format. 

The first and last numbers in the 26-bit Wiegand format are beginning and ending bits known as parity bits. They are not part of the unique identification laid out in the code. Bits two through nine make up the facility code. The facility code consists of eight bits. Bits 10 through 25 make up the ID number. The ID number consists of 16 bits. 

Here is how the code in 26-bit Wiegand appears when P stands for parity bit, F stands for facility code bit, and I stands for ID number bit: 

PFFFFFFFFIIIIIIIIIIIIIIIIP

The 26-bit Wiegand format allows for 256 possible facility codes and 65,535 possible ID numbers. When combining both unique identifiers, this allows for 16,711,425 unique access cards. 

Rather than being written out with numbers or letters as in the example above, the code is represented in an access card or other access device with a series of wires. We’ll explain more about how that works below.

How Does 26-Bit Wiegand Format Work? 

Back in the 1970s, Weigand discovered that cobalt, iron, and vanadium alloy wires switch polarity when they enter a magnetic field. He also found that sensor coils can pick up the change in polarity. This laid the groundwork for the modern Weigand protocol where access card readers are able to translate and read the code that lies hidden in the wires inside access devices. 

John Wiegand
John Wiegand

26-bit Wiegand access cards have three wires inside: data low (data0), data high (data1), and a ground wire. Because binary numbers are expressed as 0 or 1, data0 and data1 are used to create those binary numbers that the access control system can read. When the data0 wire transmits a signal, the computer reads it as 0, and when the data1 wire transmits a signal, the computer reads it as 1. The wires are uniquely designed to create a different code for each cardholder.

When a device that’s encoded with the format passes through the field of a card reader, it picks up on the unique sequence of bits contained in the device. Then, it grants access if the facility code and ID number in the device are allowed access. Of course, the system can also deny access if the code in the card or other access device does not match an approved code. 

Where Is the 26-Bit Wiegand Format Used?

The 26-bit Wiegand format is most often used in standard access control systems. You’ll find wires corresponding to the 26 bits in access cards, key fobs, fingerprint readers, and other access control devices. 

card reader door lock

The data on a standard Wiegand-formatted device is not encrypted. This, of course, presents a vulnerability and is one of the reasons this format has lost some of the popularity it previously held. It’s also possible for duplicate 26-bit Weigand access devices to exist, which is a major concern for industries that highly value security. 

You’ll often find access control systems that use the 26-bit Wiegand format in older buildings because it was once the gold standard. Unless there is a malfunction in the equipment, there isn’t often an immediate need for companies to upgrade to a different format even though the 26-bit Wiegand format is becoming a bit outdated. It still works very well for most use cases. 

However, newer buildings and newer access control systems are beginning to favor different formats, such as Open Supervised Device Protocol (OSDP). This can increase security because it is encrypted. For this reason, you’re also less likely to find 26-bit Wiegand formats in buildings and campuses where security is of utmost importance. 

Nonetheless, the 26-bit Wiegand format is still used today for many reasons. It’s easy to use, it’s readily available, and most card readers and access control systems are equipped to read the format. If you purchase or install an access control system and you don’t specify or request a particular format, it’s likely your system uses the 26-bit Wiegand format.

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