Does the SSN have a check digit?

No. Unlike many national ID numbers, the US Social Security Number has no mathematical check digit. Validity is determined purely by structural rules — the area must be 001–899 and not 666, the group must be 01–99, the serial must be 0001–9999, and the number must not be a reserved or publicly advertised number.

Does a valid format mean the SSN was really issued?

No. Because there is no checksum, this tool can only confirm that a number follows the SSA's published format and exclusion rules. It cannot confirm a number was actually issued to a person, and it never queries any government system.

Is my SSN sent anywhere?

No. The validator is privacy-first. All checks run locally in your browser with JavaScript — there are no network requests and your SSN never leaves your device.

What does the AAA-GG-SSSS structure mean?

An SSN is nine digits split as a 3-digit area number, a 2-digit group number and a 4-digit serial number. Since 2011 the SSA assigns these randomly, so the area no longer indicates the state of issue.

Why is 666 not allowed as an area number?

The SSA has never issued area numbers of 000, 666, or 900–999. 666 is permanently excluded, so any SSN whose first three digits are 666 fails the structural check.

What is the 078-05-1120 number?

It is the most famous publicly advertised SSN, printed on a sample card in Woolworth wallets from 1938 and used by thousands of people by mistake. The SSA voided it, so it and a few other promotional numbers (e.g. 219-09-9999, 457-55-5462) are permanently invalid.

Can I tell where or when an SSN was issued?

No longer. Before mid-2011 the area number broadly reflected the state of application, but the SSA's switch to randomized assignment removed any geographic meaning, so the number reveals nothing reliable about location or date.

Does this tool tell me who an SSN belongs to?

No. It only checks structure and exclusion rules. There is no public lookup, and the tool never queries any government database — it cannot identify a person or confirm a number was issued.

US SSN Format Validator — Check Social Security Number Structure

US SSN format validator

A US Social Security Number (SSN) is the nine-digit number issued by the Social Security Administration (SSA) for tax and benefit purposes. It has no mathematical check digit, so a number can only be checked against the SSA’s published structure and exclusion rules — which is exactly what this tool does, entirely in your browser. It is useful for catching typos in forms and test data, not for confirming that a real SSN was issued.

How it works

An SSN is written AAA-GG-SSSS: a 3-digit area, a 2-digit group and a 4-digit serial. The validator strips dashes and spaces, then applies four checks:

Part	Digits	Valid range	Excluded
Area	1–3	001–899	000, 666, 900–999
Group	4–5	01–99	00
Serial	6–9	0001–9999	0000
Reserved	all 9	—	advertised numbers (e.g. 078-05-1120)

It also rejects a short list of publicly advertised / promotional numbers the SSA permanently voided, such as 078-05-1120, 219-09-9999 and 457-55-5462.

Example

Take 123-45-6789. The area 123 is within 001–899 and is not 666, the group 45 is within 01–99, and the serial 6789 is within 0001–9999, and it is not a reserved number — so the format is valid. By contrast 666-45-6789 fails on the very first check, because 666 is never issued.

Privacy-first: every check runs in your browser. Nothing is uploaded, stored or sent to any server, and this tool does not query any government database.