SSN Format Checker

Check whether a 9-digit number matches the U.S. Social Security Administration's basic structural formatting rules — area, group, and serial number ranges. No install, no sign-up, runs entirely in your browser.

🔒 Privacy: The number you enter is checked only by JavaScript running in your own browser. It is never sent to a server, never saved, and never written into the page's URL. This is not an SSA lookup or identity-verification service — it only checks digit-format rules.

Social Security Number

Type 9 digits — dashes are added automatically. Nothing is stored or transmitted.

Try an example:

123-45-6789 valid format 666-12-3456 invalid area 078-05-1120 famous "advertised" #

Quick answer A Social Security Number cannot be mathematically "verified" the way an IBAN or a Turkish national ID can — it has no checksum digit. The only thing that can be checked from the digits alone is structural format: exactly 9 digits as XXX-XX-XXXX, an area number that isn't 000/666/900–999, a group number that isn't 00, and a serial number that isn't 0000. Passing these checks means the number is structurally plausible — nothing more. Confirming a real SSN requires the Social Security Administration's own official verification channels.

9 digitsTotal length: XXX-XX-XXXX

3Area ranges never issued (000, 666, 900–999)

0Public checksum digits (none exist)

100%Client-side processing

⚠️ Important — scope & privacy note: This tool performs a structural format check only. A "valid format" result does not prove the number is a real, currently issued, or active Social Security Number, and it does not confirm ownership by any person. It is not a Social Security Administration lookup, credit check, or identity-verification service. All processing happens locally in your browser — the number you type is never sent to a server, logged, or stored. For legitimate SSN verification, employers and authorized parties should use the SSA's official Consent Based SSN Verification (CBSV) service.

🔢 SSN Format Checker — ToolPico ↗

How is a Social Security Number formatted, and why isn't there a checksum?

A full explanation of SSN structure — area, group, and serial numbers — why no mathematical check digit exists, and what "format valid" actually means.

A Social Security Number (SSN) is a 9-digit number the U.S. Social Security Administration (SSA) assigns to track individuals for Social Security and tax purposes. It's written as three groups — XXX-XX-XXXX — historically called the area number, group number, and serial number. Unlike numbering systems that embed a mathematical check digit computed from the other digits (so a computer can confirm the number is internally consistent), an SSN has no such formula. This tool checks only the structural rules described below — it never invents or applies a checksum, because none exists.

What do the three parts of an SSN mean?

Quick answerThe area number (first 3 digits) is the broadest grouping; the group number (middle 2 digits) subdivides it; the serial number (last 4 digits) is assigned sequentially within a group. Before June 2011 the area number generally reflected the state where the number was first requested. Since the SSA's 2011 randomization policy, area numbers no longer carry geographic meaning and are assigned without a fixed state pattern — but the same never-issued ranges still apply.

Which ranges does the SSA say it never issues?

Quick answerThe SSA has publicly documented that it never issues area number 000, never issues area number 666, and never issues any area number in the 900–999 range. It also never issues a group number of 00 or a serial number of 0000. Any number that falls into one of these ranges is guaranteed to be structurally invalid — this is real, public SSA numbering information, not a guess.

Area = 000: reserved, never assigned to anyone.
Area = 666: reserved and skipped in SSA's numbering scheme.
Area = 900–999: reserved for other purposes (such as ITIN-adjacent uses), never issued as an SSN.
Group = 00 or Serial = 0000: never issued in either position.

Why can't this — or any — tool confirm a real SSN?

Quick answerConfirming that a specific SSN is real and belongs to a specific person requires checking it against the Social Security Administration's own records — something only the SSA (or a service it authorizes, like CBSV) can do. Because SSNs have no public checksum, any 9-digit number that avoids the never-issued ranges is structurally indistinguishable from a real one using math alone. Format checks like this one narrow down obviously-fake numbers; they cannot, and do not claim to, confirm authenticity.

Note: These rules check the number's structure only. A number passing every rule below is not proof that a person exists or that the number is theirs — official identity or SSN confirmation must go through the SSA's authorized channels, never a public website.

SSN format rules reference

A citable quick reference: the structural rules this tool checks, and the area-number ranges the SSA has never issued.

Structural format rules checked by this tool
Rule	Requirement	Example that fails
Total length	Exactly 9 digits, digits only	12345678 (8 digits)
Grouping	Read/entered as 3-2-4 (area-group-serial)	XXX-XX-XXXX
Area number	Not 000, not 666, not 900–999	666-12-3456
Group number	Not 00	123-00-4567
Serial number	Not 0000	123-45-0000

Source: Social Security Administration public numbering guidelines. There is no additional checksum digit beyond these structural rules.

Area number (first 3 digits) status
Area range	Status	Note
000	Never issued	Reserved; not assigned to anyone
666	Never issued	Reserved and skipped by the SSA
900–999	Never issued	Reserved for other uses, never assigned as an SSN
001–899 (excluding 666)	Potentially valid range	Could theoretically be issued (pre- or post-2011 randomization)

"Potentially valid range" means the number is not automatically ruled out by structure — it is not confirmation that the number has actually been issued.

SSN format glossary

Short definitions of the core terms used in SSN structure and format checking.

Social Security Number (SSN)A 9-digit number assigned by the SSA to track individuals for Social Security and tax purposes.

Area numberThe first 3 digits of an SSN; historically state-linked, randomized nationwide since June 2011.

Group numberThe middle 2 digits of an SSN, subdividing the area number.

Serial numberThe last 4 digits of an SSN, assigned sequentially within a group.

Checksum / check digitA digit mathematically derived from the others to self-validate a number. SSNs do not have one.

Format validationChecking that a number's structure follows the issuing rules — not the same as confirming it is real.

SSN randomization (2011)SSA policy since June 25, 2011 assigning SSNs randomly nationwide instead of by state.

CBSVConsent Based SSN Verification — SSA's official paid service for authorized real SSN verification.

ITINIndividual Taxpayer Identification Number — a separate 9-digit IRS number for tax filing, not an SSN.

Never-issued rangeAn area/group/serial value the SSA has publicly confirmed it will never assign (e.g. area 000, 666, 900–999).

In-depth guides

Detailed answers to the most common questions about SSN structure and verification.

Why doesn't a Social Security Number have a check digit?

Many numbering systems — credit card numbers, IBANs, and some national ID numbers — include one or more digits computed from a formula applied to the rest of the number, so a computer can instantly catch a typo or transposition. The Social Security Administration never built this into the SSN. SSNs were designed in the 1930s purely as sequential record-keeping identifiers, and even after the 2011 move to random assignment, no check-digit formula was added.

Practically, this means no calculation exists that can look at 9 digits and mathematically prove they form a real SSN. The best any tool — including this one — can do is rule out numbers that fall in ranges the SSA has publicly confirmed it never issues.

What is SSA's Consent Based SSN Verification (CBSV), and who can use it?

CBSV is the Social Security Administration's official service that lets registered, authorized companies check — with the number holder's written consent — whether a submitted name, date of birth, and SSN match SSA's own records. It returns a simple match/no-match result and charges a per-verification fee; it is aimed at businesses with a legitimate, consented need (such as background-check or payroll providers), not individual members of the public.

If you need to confirm that an SSN actually belongs to someone, CBSV (or an equivalent authorized SSA channel) is the legitimate path — a free format-checking tool like this one, or any similar public website, cannot substitute for it.

How did SSN assignment change with 2011 randomization?

From the program's start until June 25, 2011, the first three digits (area number) of a newly issued SSN generally corresponded to the state where the application was filed, and the remaining digits were assigned in a semi-predictable order within that state's allocation. This made the total pool of numbers for some states easier to project and, over time, closer to exhaustion.

Since June 25, 2011, the SSA assigns all newly issued SSNs randomly across the entire pool of available numbers nationwide — a policy commonly called SSN randomization. Area numbers no longer indicate a state, and previously unassigned area numbers became available for use — with 000, 666, and 900–999 remaining permanently off-limits.

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Frequently asked questions

Does a Social Security Number have a checksum digit?

No. Unlike some other ID or account numbering systems that include a mathematical check digit, a U.S. Social Security Number has no public checksum formula. SSNs are assigned sequentially or randomly by the Social Security Administration with no self-validating digit, so there is no equation that can confirm an SSN is authentic just by looking at its digits.

How can I check if an SSN is valid?

You can only check whether it matches basic structural format rules: exactly 9 digits grouped as XXX-XX-XXXX, an area number outside the never-issued 000, 666, and 900–999 ranges, a group number that isn't 00, and a serial number that isn't 0000. Passing all of these means the number is structurally plausible — not that the SSN is real, active, or belongs to a specific person. Confirming that requires the SSA's official verification channels.

What area numbers (first 3 digits) are never issued?

The SSA has publicly stated it never issues area number 000, never issues 666, and never issues any number in the 900–999 range. Any SSN starting with one of these is guaranteed to be structurally invalid, regardless of the remaining digits.

Can the group number (middle 2 digits) be 00?

No. A group number of 00 has never been issued by the SSA, so a number containing 00 in that position fails the structural format check.

Can the serial number (last 4 digits) be 0000?

No. A serial number of 0000 has never been issued, so a number ending in 0000 fails the structural format check regardless of the area and group numbers.

Does this tool verify that an SSN belongs to a real person?

No, and no public web tool legitimately can. This checker only tests whether the digits fall within ranges the SSA could theoretically issue. It cannot and does not confirm the number is currently issued, unused, or belongs to any individual. Real verification requires the SSA's official Consent Based SSN Verification (CBSV) service or an equivalent authorized channel — never a public website.

Is my number sent to a server when I use this tool?

No. All checking happens locally using JavaScript running in your own browser. The number you type is never transmitted to a server, never stored, and never written into the page's URL. Closing or reloading the tab clears everything you entered.

What is SSA's Consent Based SSN Verification (CBSV)?

CBSV is the Social Security Administration's official fee-based service that lets registered, authorized companies verify — with the number holder's consent — whether a name, date of birth, and SSN match SSA records. It is the legitimate way to confirm an SSN is real; this free browser tool is not a substitute for it and does not connect to SSA systems in any way.

Why did the SSA start randomizing SSN assignment in 2011?

Before June 25, 2011, the area number generally corresponded to the state where the SSN was issued, which made the numbering pool predictable and easier to exhaust in some states. Since then, the SSA has assigned SSNs randomly nationwide ("SSN randomization") to extend the number pool and remove the geographic meaning of the area number — while still keeping 000, 666, and 900–999 permanently unissued.

What's the difference between format validation and identity verification?

Format validation only checks whether a number's digits follow structural rules — length, grouping, and which ranges are never issued. Identity verification confirms that a specific number is real, currently active, and actually belongs to the person presenting it, which requires checking against the issuing authority's own records. This tool performs format validation only; it is not, and cannot function as, an identity verification service.

Why is 078-05-1120 called the "advertised" or "sample" Social Security Number?

In the 1930s, a wallet manufacturer inserted a sample Social Security card printed with the number 078-05-1120 into wallets sold in stores nationwide as a display prop. Many buyers mistook the card for their own real SSN and began using it, and over the following decades it was claimed by thousands of people, becoming the most misused Social Security Number in U.S. history. It passes ordinary structural format checks — its area, group, and serial numbers all fall in technically issuable ranges — which is exactly why it is offered here as a one-click cautionary example, not a number anyone should submit or treat as their own.

Methodology & sources

ToolPico's SSN Format Checker is a free, independent tool. It applies only the structural rules the Social Security Administration has made public: exactly 9 digits (area 3 + group 2 + serial 4), an area number outside 000/666/900–999, a group number other than 00, and a serial number other than 0000. No checksum or check-digit algorithm is computed or applied anywhere in this tool, because the SSA has never defined one for SSNs.

Sources: Social Security Administration public numbering and randomization guidance · SSA: SSN Randomization · SSA: Consent Based SSN Verification (CBSV). Last updated: July 21, 2026.

Scope & limits: Results describe structural plausibility only and are provided for informational purposes. They are never a substitute for the SSA's own records or its official CBSV verification channel, and they must not be used to claim, imply, or assume that any number is a real, active, or specific person's Social Security Number.

How is a Social Security Number formatted, and why isn't there a checksum?

What do the three parts of an SSN mean?

Which ranges does the SSA say it never issues?

Why can't this — or any — tool confirm a real SSN?

SSN format rules reference

SSN format glossary

In-depth guides

Add this checker to your site (embed code)

Frequently asked questions

Methodology & sources

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