SSN Validator: Check Social Security Number Format

How to use the ssn validator

1. Type or paste a nine-digit number into the field, using either 123-45-6789 or 123456789 format.
2. The SSN validator checks that the input is nine digits or the standard hyphenated layout.
3. It checks the area, group and serial numbers against current SSA rules.
4. Review the rule table to see exactly which check passed or failed.

How the SSN format rules work

A US Social Security Number contains nine digits split into three parts: the area number (first three digits), the group number (middle two digits) and the serial number (last four digits). Since the SSA introduced randomization on June 25, 2011, the area number no longer corresponds to a geographic region. Instead, the following rules determine whether a number has a valid format:

• The area number cannot be 000, 666, or anything from 900 to 999.
• The group number cannot be 00.
• The serial number cannot be 0000.

For example, take the input 123-45-6789. The area is 123 (not 000, 666 or 900+), the group is 45 (not 00) and the serial is 6789 (not 0000). Every rule passes, so this social security number validator reports a valid format.

Common invalid patterns

The table below shows inputs that fail specific rules. Use these as test cases when building forms or writing validation logic.

Only two layouts are accepted: nine digits (123456789) or the standard 123-45-6789 with hyphens after the third and fifth digits. Any other layout, including extra or misplaced hyphens, letters or spaces, is reported as invalid format.

Format validation versus issuance verification

This tool is a format checker. It confirms that a string of digits follows the structural rules published by the Social Security Administration. It does not query any government database, and it cannot tell you whether a particular number was actually issued to a person. If you need to verify identity or employment eligibility, use the official E-Verify system or contact the SSA directly.

Developers often pair an SSN checker with other validation utilities. For instance, a credit card validator uses the Luhn algorithm to confirm payment card numbers, while an IBAN validator checks international bank account formats. Each tool verifies structure, not account status.

The Woolworth wallet number

The number 078-05-1120 is one of the most famous Social Security Numbers in history. In 1938, the E.H. Ferree Company inserted a sample card bearing this number into wallets sold at Woolworth stores to demonstrate how the new cards would fit. Thousands of people began using it as their own, and the SSA eventually had to void it. Despite being retired, 078-05-1120 still passes every structural rule in this SSN validator because its area (078), group (05) and serial (1120) are all within the allowed ranges. This illustrates why format validation alone cannot confirm that a number is active or assigned.

Using the SSN checker in development

When building web forms that collect taxpayer or employee data, client-side format validation prevents obvious typos before submission. A typical regular expression for the post-2011 rules looks like this:

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

This pattern enforces the same constraints as the tool above: it rejects areas starting with 9, the exact values 000 and 666, a group of 00 and a serial of 0000. You can adapt it to accept unhyphenated input by making the dashes optional. Always remember to validate again on the server, since client-side checks can be bypassed.

If your project requires generating placeholder data for testing, consider using a dedicated fake name generator rather than inventing numbers that might accidentally belong to someone.

Worked examples