US Social Security Number (SSN) — PII context Regex for Python

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching us social security number (ssn) — pii context, ported and verified for Python. Identity and credential patterns need both correctness and safety, since they're frequent targets for adversarial input. The snippet below is ready to drop into your Python project — whether you're validating in a Django view, a FastAPI endpoint, or a standalone data processing script.

Python Implementation

# US Social Security Number (SSN) — PII context
# ReDoS-safe | RegexVault — Identity & PII > Financial PII

import re

us_social_security_number_ssn_pii_context_pattern = re.compile(r'^(?!(?:000|666|9[0-9]{2})-|[0-9]{3}-(?:00|[0-9]{3}-0{4}))(?:[0-9]{3})-(?:[0-9]{2})-(?:[0-9]{4})$')

def validate_us_social_security_number_ssn_pii_context(value: str) -> bool:
    return bool(us_social_security_number_ssn_pii_context_pattern.fullmatch(value))

# Example
print(validate_us_social_security_number_ssn_pii_context("123-45-6789"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Identity & PII > Financial PII category and carries a ReDoS-safe certification. That matters for Python developers because particularly important in Python web servers where CPU-bound regex operations can stall concurrent request handling. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

Intentionally included in Identity & PII batch in addition to Finance batch (fin-tax-01) to ensure Aurora surfaces the appropriate data handling warnings in both contexts. SSN is the most sensitive financial PII in the US — its exposure enables identity theft.