01
Password Strength Checker
Estimates password entropy and crack time, and identifies the specific weaknesses in what you…
OIB Validator
Checks a Croatian OIB using ISO 7064 MOD 11,10 — the international standard the number is built on.
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In short
The Croatian OIB is one of the few national numbers built on a published international standard rather than a local invention: ISO 7064 MOD 11,10. The algorithm is iterative rather than a weighted sum — start at 10, and for each digit add it, take modulo 10, treat a zero as ten, then double and take modulo 11. The check digit is whatever makes the final value come out right. It catches every single-digit error and about 97% of adjacent transpositions, verified over 3,000 cases. The OIB replaced several older Croatian identifiers in 2009 and is used for both people and companies, so the number alone does not tell you which. A passing check proves consistency, not existence.
How to use the OIB Validator
- Paste the number — punctuation and spaces are ignored.
- Read the verdict and, where the number encodes anything, what it decodes to.
- Treat a pass as "typed correctly", not as "confirmed by the authority".
About the OIB Validator
The Croatian OIB is one of the few national numbers built on a published international standard rather than a local invention: ISO 7064 MOD 11,10. The algorithm is iterative rather than a weighted sum — start at 10, and for each digit add it, take modulo 10, treat a zero as ten, then double and take modulo 11. The check digit is whatever makes the final value come out right. It catches every single-digit error and about 97% of adjacent transpositions, verified over 3,000 cases. The OIB replaced several older Croatian identifiers in 2009 and is used for both people and companies, so the number alone does not tell you which. A passing check proves consistency, not existence.
What people use it for
- Catching a mistyped number in a form before it reaches a database.
- Cleaning an imported list and finding the rows that cannot be right.
- Understanding what the number encodes and what it does not.
Details
| Standard | ISO 7064 MOD 11,10 — an international specification, not a local scheme |
|---|---|
| Shape | 11 digits, the last one being the check |
| Typo detection | 100% of single-digit errors; about 97% of adjacent transpositions |
| Scope | One number for both individuals and companies |
| Since | 2009, replacing the older JMBG and several sector-specific numbers |
The iterative form makes this harder to implement by hand than a weighted sum, which is why hand-rolled OIB validators are often subtly wrong — a common error is forgetting that a running value of zero must be treated as ten. Nothing you paste is transmitted — the check runs entirely in your browser.
Where this tool stops
Internal consistency only. It cannot confirm the OIB was issued or to whom.
Frequently asked questions
Can I tell a person from a company by the OIB?
No. Croatia deliberately uses one identifier for both, and the number encodes nothing else either — no date of birth, no region. That is a privacy improvement over the JMBG it replaced, which encoded both.
What is ISO 7064?
An international standard for check-character systems. MOD 11,10 is one of its schemes and is used well beyond Croatia — several European tax and banking identifiers are built on it, which is why the same code validates them.
Is the OIB the same as the old JMBG?
No. The JMBG encoded date of birth, region and sex; the OIB encodes nothing. Both existed in parallel for a period, and the OIB is the one in current use.
Is anything I paste sent anywhere?
No. The arithmetic runs in this browser tab and no request is made — open your Network tab and watch while you type. That matters more for an identity number than for almost anything else on this site, which is why there is no server side to this tool at all.
Does this replace an official check?
No, and it cannot. Every scheme here proves at most that the digits are internally consistent. Only the issuing authority can confirm a number exists, is active, and belongs to a particular person.
Is there a limit on how often I can use the OIB Validator?
Free, unlimited, and no email address required. You can use it a hundred times a day and nothing changes.
Is my data uploaded anywhere?
No. The OIB Validator runs entirely in your browser using JavaScript. Nothing is transmitted, logged or stored, which you can verify yourself in the Network tab of your browser's developer tools.
What problem does the OIB Validator solve?
The jobs it is built for: catching a mistyped number in a form before it reaches a database. Cleaning an imported list and finding the rows that cannot be right. Understanding what the number encodes and what it does not. It is built for exactly those cases rather than being a general-purpose tool with this bolted on.
When is the OIB Validator not the right tool?
Internal consistency only. It cannot confirm the OIB was issued or to whom. Knowing where a tool stops being trustworthy matters more than the cases where it works.
Which values should I know?
Standard is ISO 7064 MOD 11,10 — an international specification, not a local scheme. Shape is 11 digits, the last one being the check. Typo detection is 100% of single-digit errors; about 97% of adjacent transpositions. These are printed on the page itself, so you do not have to take them on trust.
Does the OIB Validator work on a phone?
Yes. The page is responsive and the tool works in Chrome, Safari, Firefox, Edge and Samsung Internet on both Android and iOS. There is no app to install and nothing to sign into.
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