# Postcode area

The postcode area is the neighbourhood a written town is checked against when it is not one of the postcode's own places: the letters of a British outward code, the first three digits of a ZIP.

Date: 2026-09-16

Updated: 2026-09-24

The postcode area is the neighbourhood a written town is checked against when it is not one of the places the directory lists under the postcode itself: the letters of a British outward code, the first three digits of a US ZIP, and the first two characters of a postcode everywhere else.

## What Spaw answers

`locality_matches_postcode` is strict: `true` only when the town is one the directory publishes for that postcode. When it is `false`, the town is looked for among every place the directory lists across the postcode area. A hit sets `confirmation.locality` to `postcode_area` and adds no weight, because a post town written for a settlement — Reading for a Woodley postcode, Toronto for a district the Canadian directory names by its neighbourhood — is how envelopes are addressed, not an error. Where the postcode's region is a single city — Mexico City, Delhi, Jakarta, Bangkok, Moscow, Seoul and Tokyo's wards among them — the region's own name (Distrito Federal for 06000, Tokyo for 100-0005) reads `postcode_area` too, reported and never scored. Only a town found nowhere in the area carries the `locality_mismatch` weight of +30, and only where the directory lists every place a postcode is written with; a directory that carries one default place per code, as the United States one does, reports the mismatch and never scores it.

## What it is not

It is not a claim that the town is right. `postcode_area` means the directory knows the name in the vicinity; the strict field beside it still says the postcode's own places did not include it.

Reference: https://spaw.co/glossary/postcode-area