The 26-bit Wiegand format is one of the most widely used standards for access control systems, particularly in legacy installations.
It’s an open format, meaning that any organization can implement and use it, and multiple manufacturers produce cards compatible with this system.
What Is the Standard 26-Bit Wiegand Format?
At its core, the 26-bit Wiegand format is a method of encoding binary data to identify individuals via access cards, key fobs, or other devices.
The term “bit” refers to the smallest data unit, either a 0 or a 1, which makes up the digital code stored on these cards. The format follows a structured design where the data is split into three main components:
- Bits: The first and last bits in the 26-bit sequence are parity bits. These are used for error checking to ensure the data is transmitted correctly, but they do not contribute to the unique identification number on the card.
- Facility Code: The second through ninth bits (8 bits in total) represent the facility code or site code. This code identifies the specific location or organization that issued the card. The facility code can range from 0 to 255, allowing for 256 unique facility codes.
- Card Number: Bits ten through twenty-five (16 bits) store the ID number assigned to the individual cardholder. This number can range from 0 to 65,535, meaning there can be over 65,000 unique cardholders per facility.
The 24 data bits can represent 16,777,216 facility-code/card-number pairs: 256 × 65,536. This is a mathematical capacity, not a guarantee of unique issued credentials; systems may reserve values such as zero.
How Does the 26 Bit Wiegand Format Work?
An RFID card communicates wirelessly with a compatible reader. D0, D1 and ground are part of the Wiegand connection between the reader and controller; they are not wires inside an RFID card.
The reader sends pulses on D0 for a binary zero and D1 for a binary one. The controller interprets the configured bit layout and applies the access permissions; parity provides error checking, not encryption.
Why Is the Wiegand 26-Bit Format Still in Use in Access Control?
H10301 remains useful where an existing controller supports that format and its numbering capacity meets the site requirements. Confirm the reader technology and controller configuration before ordering cards.
A 26-bit number does not define the card frequency or its security features. Legacy Wiegand reader wiring does not provide encrypted transport; SIA’s OSDP protocol supports a secure channel between the reader and controller when configured appropriately.
OSDP is a reader-to-controller communication protocol, not a replacement card-number layout. You must assess credential security and reader wiring separately.
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How to Identify if Your System Uses the 26-Bit Wiegand Format
To determine whether your access control system or card uses the 26-bit Wiegand format:
Check the Documentation
The easiest way is to check the system or card documentation, which often includes details on the card format, facility code, and card range.
Look for the H10301 Identifier
The H10301 format is a common name for the 26-bit Wiegand format. If this is listed on your card packaging or system, it confirms that the format is in use.
Consult Your Access Control Provider
If you’re unsure about the format, contact your access control provider. They can usually confirm the card format based on the equipment and system configuration.
Use a Card Reader
Use a reader that supports the credential technology and reports the required data. A 26-bit readout alone does not prove H10301; confirm the facility-code field, card-number field and parity layout against the system configuration.
For the numbering layout, see HID’s Understanding Card Data Formats guide and our H10301, H10302 and H10304 comparison.
