Postcodes

Postcodes are codes used by postal services to identify geographic areas for the purposes of sorting and delivering mail. They are typically assigned to addresses or small groups of addresses and may include letters, numbers, or a combination of both. Beyond mail routing, postcodes are used in logistics, demographics, market research, and navigation systems.

Formats vary by country. In the United Kingdom, postcodes combine an outward code and an inward code (for example SW1A 1AA), reflecting a hierarchical geography that can identify town, street, and even a single building. In the United States, ZIP codes are five digits, with ZIP+4 adding a hyphen and four more digits to pinpoint a small locality or even a single block. Canada uses a six-character format with a space (A1A 1A1); Australia uses four digits (e.g., 2000). Other countries use alphanumeric systems, such as those in many European nations.

Origins date to the expansion of postal networks in the 19th and 20th centuries. Postcodes improve automated sorting by machines and support address verification in databases. They can also facilitate routing analytics, insurance pricing, and disaster response planning, though they may change over time as populations shift or administrative boundaries are altered.

Today, postcodes are embedded in address databases, maps, and e-commerce systems. While primarily a postal tool, their use extends to geocoding, census statistics, and location-based services. Different countries maintain separate postcode structures and update them through national postal authorities.