MaxiCode

MaxiCode symbols using modes 2 and 3 include a Structured Carrier Message containing key information about a package. This information is protected with a strong Reed-Solomon error correction code, allowing it to be read even if a portion of the symbol is damaged. These fields include:

1. A 4-bit indication of the mode in use, currently either mode 2 or mode 3.
2. A national or international postal code. MaxiCode supports both numeric postal codes (e.g. a ZIP Code), and alphanumeric postal codes.
3. A 3-digit country code encoded per ISO 3166
4. A 3-digit class of service code assigned by the carrier

The structured portion of the message is stored in the inner area of the symbol, near the bull's-eye pattern. (In modes that do not include a structured portion, the inner area simply stores the beginning of the message.)

Irrespective of mode, a variable amount of application-specific information can be encoded in a MaxiCode symbol. This format of this additional data is not strictly defined, and amongst other information may include:

• Purchase order number
• Customer reference
• Invoice number
• Tracking number
• Indicator of the originating carrier

• Mode 0, Obsolete; replaced by Modes 2 and 3. Older printers with outdated firmware may still produce it. Identifiable by two white horizontal hexagons in the upper right corner (black in all other modes).
• Mode 1, Obsolete; replaced by Mode 4.
• Mode 2, Structured Carrier Message with numeric postal code (mainly for U.S. domestic use).
• Mode 3, Structured Carrier Message with alphanumeric postal code (mainly for international use).
• Mode 4, Unformatted data with Standard Error Correction.
• Mode 5, Unformatted data with Enhanced Error Correction.
• Mode 6, Used for programming hardware devices.

UPS labels use Mode 2 or 3 MaxiCodes.