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Regex: US ZIP code

A US ZIP code is five digits, optionally followed by a dash and four more (ZIP+4), as in 10001-1234. The pattern accepts exactly those two forms.

Open in Regex Tester The pattern and every example below are filled in.

Pattern

^\d{5}(?:-\d{4})?$

How it works

^
Start of the string.
\d{5}
Five digits.
(?:-\d{4})?
Optionally, a dash and four more digits.
$
End of the string.

Matches

  • 90210
  • 10001-1234
  • 00501

Doesn't match

  • 9021
  • 902101
  • 90210-12
  • ABCDE

In your language

JavaScript
/^\d{5}(?:-\d{4})?$/

A literal; new RegExp(source, flags) builds the same from a string.

Python
re.compile(r"^\d{5}(?:-\d{4})?$", re.ASCII)

A raw string, so backslashes reach re as written. re.ASCII keeps \d to 0-9, as in JavaScript (Python matches any Unicode digit otherwise). Use re.fullmatch to test a whole string.

Java
Pattern.compile("^\\d{5}(?:-\\d{4})?$")

A normal string literal, so every backslash is doubled. matcher(s).matches() tests the whole string.

Go
regexp.MustCompile(`^\d{5}(?:-\d{4})?$`)

A raw string in backticks. RE2 runs in linear time but has no lookaround and no backreferences.

PHP
preg_match('/^\d{5}(?:-\d{4})?$/D', $input)

PCRE with / delimiters inside a single-quoted string. Without the D modifier, $ also matches before a final newline, so it is added to patterns that end in $.

C#
new Regex(@"^\d{5}(?:-\d{4})?$", RegexOptions.ECMAScript)

A verbatim string: backslashes stay, a quote is doubled. RegexOptions.ECMAScript keeps \d to 0-9, as in JavaScript. $ also matches before a final newline; to reject one, end the pattern with \z instead.

Common mistakes

  • Store ZIP codes as text

    ZIP codes in New England start with 0 (02108 is in Boston). Stored as a number, the leading zero is lost and 2108 no longer matches.

  • Shape is not existence

    Fewer than half of the possible five-digit codes are in use. Only a lookup against USPS data tells you a code is real.

  • Other countries, other shapes

    Canada writes A1A 1A1 (^[A-Z]\d[A-Z] ?\d[A-Z]\d$), Poland 00-950 (^\d{2}-\d{3}$), and the UK has several shapes such as SW1A 1AA. Choose the pattern from the address's country.