Blog
Platforms
Country, State, ZIP: filling a cross-border address form without guessing
The same address form changes shape when you switch from the US to the UK, Japan or Germany. A field-by-field guide to leading zeros, state codes, ZIP+4 and outcodes.
Data notes
One post code, nine towns: the trap in every post code dataset
German code 01945 maps to nine places, while 11010 exists in 15 countries. Why a post code is a delivery area, not an address — with real examples from the data.
Formats & rules
Five post code systems, explained: ZIP, postcode, 7-digit, 5-digit and FSA
Post codes are not a global standard. Here is how US ZIP, UK postcode, Japan's 7-digit code, Germany's 5-digit code and Canada's FSA actually work, with real examples.