Regular expression
/^\d{5}(?:-\d{4})?$/Pattern breakdown
| Part | Meaning |
|---|---|
Anchor or context | Use anchors when you need whole-string validation. |
Main token | The core token sequence describes the accepted text shape. |
Character class | Character classes limit which characters are valid. |
Quantifier | Quantifiers control how many characters or groups are accepted. |
Flags | Use language-specific flags such as i, m, or u only when needed. |
Should match
94105-1234
Should not match
9410not matching sample94105-1234 invalid941094105-1234
Test cases
| Input | Expected | Why it matters |
|---|---|---|
94105-1234 | Match | Representative valid input for this pattern. |
9410 | No match | Common invalid or boundary input. |
(empty string) | No match | Common invalid or boundary input. |
not matching sample | No match | Common invalid or boundary input. |
94105-1234 invalid | No match | Common invalid or boundary input. |
941094105-1234 | No match | Common invalid or boundary input. |
JavaScript
const re = /^\d{5}(?:-\d{4})?$/;
re.test(input);Python
import re
bool(re.search(r"^\d{5}(?:-\d{4})?$", text))PHP
$ok = preg_match('/^\d{5}(?:-\d{4})?$/', $value) === 1;Java
Pattern pattern = Pattern.compile("^\\d{5}(?:-\\d{4})?$");
pattern.matcher(value).find();Go
re := regexp.MustCompile(`^\d{5}(?:-\d{4})?$`)
ok := re.MatchString(value)Notes and production use
US ZIP Code regex is useful as a practical starting point. Test it against your real input, avoid using it as the only security control, and prefer a parser when the format has complex grammar.
Performance tip: avoid running complex regular expressions repeatedly on very large untrusted strings without limits. Prefer anchored validation patterns, cap input length before matching, and use a parser when the target format has nested grammar.