우편 바코드: POSTNET, Intelligent Mail 및 Royal Mail
A tour of postal barcode symbologies used by USPS, Royal Mail, and Australia Post for automated mail sorting and delivery tracking.
Postal Barcodes: POSTNET, Intelligent Mail & Royal Mail
Postal services worldwide use specialized barcode symbologies to automate mail sorting, routing, and delivery tracking. These barcodes look different from retail barcodes because they use varying bar heights rather than bar widths.
USPS POSTNET (Legacy)
POSTNET (Postal Numeric Encoding Technique) was used by the US Postal Service from 1993 to 2013. It encoded ZIP codes (5, 9, or 11 digits) using tall and short bars:
- Each digit is 5 bars: 2 tall and 3 short
- Frame bars (tall) at start and end
- Read from bottom: tall = 1, short = 0
POSTNET enabled automated sorting at speeds of 30,000 pieces per hour. It was replaced by the Intelligent Mail barcode in 2013.
USPS Intelligent Mail Barcode (IMb)
The Intelligent Mail barcode replaced POSTNET and PLANET with a single, more capable format. It uses four bar types based on height:
- Tracker (T): Short, centered
- Descender (D): Short, bottom-aligned
- Ascender (A): Short, top-aligned
- Full (F): Tall, full height
IMb encodes 31 digits of data in 65 bars:
- Barcode identifier (2 digits)
- Service type (3 digits)
- Mailer ID (6 or 9 digits)
- Serial number (9 or 6 digits)
- Routing code (0, 5, 9, or 11 digits for ZIP)
IMb provides tracking capability, enabling USPS Informed Visibility and real-time delivery notifications.
Royal Mail 4-State Customer Barcode
The UK's Royal Mail uses a 4-state barcode similar in concept to IMb:
- Four bar heights encode data pairs
- Encodes the full UK postcode plus Delivery Point Suffix
- Includes a check digit
The barcode appears in the lower right of envelopes for automated sorting.
Australia Post 4-State Barcode
Australia Post uses its own 4-state barcode for mail sorting and tracking. It encodes:
- Format Control Code
- Sorting Code (postcode)
- Customer Information
- Reed-Solomon error correction
Common Characteristics
All postal barcodes share features that distinguish them from commercial barcodes:
| Feature | Postal Barcodes |
|---|---|
| Encoding | Bar heights, not widths |
| Reader | Specialized high-speed equipment |
| Speed | 30,000-40,000 pieces/hour |
| Placement | Address block area |
| Orientation | Horizontal, bottom of envelope |
| Color | Typically printed in fluorescent ink |
Implementation Notes
- Postal barcodes are typically applied by mailers using address management software
- USPS offers postage discounts for mail with Intelligent Mail barcodes
- Most commercial barcode scanners cannot read postal barcodes (they require specialized readers)
- CASS (Coding Accuracy Support System) certification ensures address and barcode quality