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There are times when you may want to use the 9 digit zip code validation for US. The 9 digit zip code is usually in format like this #####-####. For a 9 digit US zip code validation use below regular Expression. ^([0-9]{5}-[0-9]{4})$.
ZIP+4 Codes are the last 4 digits of a nine-digit ZIP Code. A complete, nine-digit ZIP Code consists of two parts. The first five digits indicate the destination post office or delivery area. The last 4 digits represents a specific delivery route within that overall delivery area. All 9 digits of a full zip code assist the USPS in effectively sorting the mail.