Open Address Ninja from Apps in your Shopify admin. On the home page, click Validate postal code format. In the Countries card, choose All countries, Only these countries, or Except these countries. Add countries with the Search countries field. Click Turn on. If you changed the countries, the button reads Save and turn on.
Address Ninja checks that customers enter the postal code in the format used by their shipping country, such as 12345 for the United States, K1A 0A6 for Canada, or SW1A 1AA for the United Kingdom. The whole field must match the format: "London SW1A 1AA" is rejected, "SW1A 1AA" passes. The formats are built in for 173 countries and cannot be edited. Countries with no postal code format are not checked. To change the error message, open the Error message card.
Use cases: Prevent shipping issues caused by malformed postal codes and make sure addresses meet the postal service requirements of each country.
Originally from our Help Center