Source & attribution
Postal data comes from GeoNames, licensed under Creative Commons Attribution 4.0 (CC BY 4.0). GeoNames is an open gazetteer; we use its postal code export and keep attribution and the license link on this page.
Method & updates
We download the GeoNames postal export, deduplicate and normalize it, then build the lookup database. Each build records the source hash and row counts; the "updated" date reflects the snapshot.
Attribution: Postal code data © GeoNames contributors, CC BY 4.0. This page links to GeoNames and the CC BY 4.0 license.