Regex for ZIP/Postal Code — Pattern Explained with Examples

This regex validates US ZIP codes in both the standard 5-digit format and the extended ZIP+4 format (5 digits, hyphen, 4 digits). It is widely used in address validation, e-commerce checkout forms, and shipping logistics systems that operate within the United States.

The Pattern

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

Pattern Breakdown

Matches

• 90210
• 12345-6789
• 10001
• 20500
• 02134
• 99501

Does NOT Match

• 1234 — only 4 digits
• 123456 — 6 digits without hyphen (too long for 5-digit, not valid ZIP+4)
• 12345-678 — ZIP+4 has only 3 digits after hyphen
• 12345-67890 — ZIP+4 has 5 digits after hyphen
• ABCD1 — contains letters
• 12345 6789 — space instead of hyphen
• 12345- — hyphen with no extension

Language Examples

JavaScript

const zipRegex = /^\d{5}(-\d{4})?$/;

console.log(zipRegex.test('90210'));        // true
console.log(zipRegex.test('12345-6789'));   // true
console.log(zipRegex.test('1234'));         // false
console.log(zipRegex.test('12345-678'));    // false

// Extract base ZIP and optional +4
const match = '12345-6789'.match(/^(\d{5})(-(\d{4}))?$/);
if (match) {
  console.log(`Base: ${match[1]}, +4: ${match[3] || 'N/A'}`);
}

Python

import re

zip_regex = r'^\d{5}(-\d{4})?$'

print(bool(re.match(zip_regex, '90210')))         # True
print(bool(re.match(zip_regex, '12345-6789')))    # True
print(bool(re.match(zip_regex, '1234')))          # False
print(bool(re.match(zip_regex, '12345-678')))     # False

# Extract parts
match = re.match(r'^(\d{5})(-(\d{4}))?$', '12345-6789')
if match:
    print(f'Base: {match.group(1)}, +4: {match.group(3) or "N/A"}')

Common Pitfalls

1. ZIP+4 hyphen is required — If you omit the ? quantifier on (-\d{4})?, the regex will reject 5-digit ZIP codes. The hyphen and extension should be optional together.

2. 5-digit only is common but limited — Many forms accept only 5-digit ZIP codes. If you exclude ZIP+4, use /^\d{5}$/ instead. For maximum compatibility, always accept both.

3. Leading zeros are valid — ZIP codes like 02134 (Boston) start with zero. The regex handles this correctly since \d{5} matches any five digits. Preserve leading zeros when storing.

4. International postal codes vary widely — This pattern is US-specific. Canadian postal codes use A1A 1A1 format, UK uses alphanumeric outward/inward codes. Do not use this pattern for international addresses.

Real-World Use Cases

• E-commerce checkout — Validating shipping address ZIP codes before calculating tax and shipping rates
• CRM address standardization — Cleaning and formatting customer address data for postal mailings
• Geocoding lookups — Extracting ZIP codes from user input to perform location-based searches

FAQ