# Postcode directory

A postcode directory is a country's list of every postcode with its status, places, region and centroid, installed whole so a missing code is an answer and not a gap.

Date: 2026-09-16

Updated: 2026-09-23

A postcode directory is a country's list of postcodes with, for each one, whether it is in use, the places it is written with, the region it lies in and a centroid — installed as a whole, so that a code the directory lacks is an answer rather than a gap in the data.

## What Spaw answers

Great Britain's directory is the ONS Postcode Directory, which carries introduction and termination dates, so `postcode_status` there can read `terminated`. Every other country's comes from the GeoNames postal-code dump under CC BY 4.0, which carries places, a region and a centroid but no dates, so a code found there is `live`. Each directory is recorded as `complete` or `partial`: only a complete one — the British directory, and the countries whose GeoNames copy reaches the operator's published total, fifteen of them on 16 September 2026 — can answer `postcode_not_found`, which makes the address invalid and free, and only about a code inside its scope: Great Britain's leaves out Northern Ireland's BT codes on licence grounds, and does not carry BFPO numbers or the BF1 and BX codes, so those are not looked up and answer `postcode_status` null. A partial directory confirms what it holds and denies nothing. The directory also feeds `locality_matches_postcode`, `administrative_area_matches_postcode` and, where no register located the building, `latitude` and `longitude` as a `postcode_centroid`. The region is compared under the names and codes people write for it, so `CDMX` matches a Mexico City postcode the directory files under the old name Distrito Federal, and `Co. Dublin` matches a Dublin routing key it files under the province of Leinster.

## What it is not

It is not an address list. A postcode identifies an area, and the streets and buildings inside it come from the national address registers, not from the directory.

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