Regex for Social Security Number — Pattern Explained with Examples

This regex validates US Social Security Numbers (SSNs) in the standard XXX-XX-XXXX format. Beyond checking the nine-digit structure with hyphens, the SSN format has specific rules about which numbers are valid: area numbers cannot be 000, 666, or 900–999, and group and serial numbers cannot be all zeros. Proper SSN validation is critical for payroll, benefits administration, and identity verification systems.

The Pattern

/^(?!000|666|9\d{2})\d{3}-(?!00)\d{2}-(?!0000)\d{4}$/

Pattern Breakdown

Matches

• 123-45-6789
• 987-65-4321
• 001-01-0001
• 999-99-9999 (hypothetical — real 999 area is not issued)
• 555-55-5555

Does NOT Match

• 123-45-678 — only 8 digits
• 123456789 — no hyphens
• 123-45-67890 — extra digit
• 123 45 6789 — spaces instead of hyphens
• ABC-DE-FGHI — non-numeric
• 000-00-0000 — area 000, group 00, serial 0000 all invalid
• 666-12-3456 — area 666 is invalid
• 987-00-1234 — group 00 is invalid

Language Examples

JavaScript

const ssnRegex = /^(?!000|666|9\d{2})\d{3}-(?!00)\d{2}-(?!0000)\d{4}$/;

console.log(ssnRegex.test('123-45-6789'));  // true
console.log(ssnRegex.test('000-00-0000'));  // false
console.log(ssnRegex.test('666-12-3456'));  // false

// Strip hyphens for storage
const raw = '123-45-6789'.replace(/-/g, '');
console.log(raw);  // 123456789

Python

import re

ssn_regex = r'^(?!000|666|9\d{2})\d{3}-(?!00)\d{2}-(?!0000)\d{4}$'

print(bool(re.match(ssn_regex, '123-45-6789')))  # True
print(bool(re.match(ssn_regex, '000-00-0000')))  # False
print(bool(re.match(ssn_regex, '666-12-3456')))  # False

# Strip hyphens
raw = re.sub(r'-', '', '123-45-6789')
print(raw)  # 123456789

Common Pitfalls

1. 000, 666, 900–999 area numbers are invalid — The SSA never issues area numbers in these ranges. The negative lookahead (?!000|666|9\d{2}) blocks them.

2. 00 group number and 0000 serial are invalid — These are never assigned. The lookaheads (?!00) and (?!0000) handle these cases.

3. SSN randomization since 2011 — In 2011, the SSA introduced randomized SSN assignment, eliminating the geographic significance of the area number. Pre-2011 area numbers corresponded to the applicant’s state of application; post-2011 they are random.

4. Dashes or no dashes — This pattern requires dashes. If you need to accept both, strip dashes first or use /^\d{9}$/ for raw format. Never display or store SSNs without encryption.

Real-World Use Cases

• Payroll processing — Validating employee SSNs for tax reporting (W-2 forms)
• Benefits enrollment — Verifying identity in healthcare or government benefits systems
• Background checks — Screening applicant SSNs against credit bureaus and public records

FAQ