01
Password Strength Checker
Estimates password entropy and crack time, and identifies the specific weaknesses in what you…
Czechia IBAN Validator
Validates a Czech IBAN: the mod-97 checksum, the 24-character length and the structure, with the bank code identified.
Security
Nothing uploaded
No sign-up
Free, unlimited
Enter something above.
In short
A Czech IBAN is exactly 24 characters: CZ, two check digits, then 4 digits, then 6 digits, then 10 digits — so the 4 characters after the check digits are the bank code — 0800 in the example — and the remaining 16 are the account number, 0000192000145399. A Czech IBAN is twenty-four characters: a four-digit bank code, then a six-digit prefix, then a ten-digit account. The prefix is a genuine part of the number and dropping it is the most common way a Czech transfer fails. The checksum is ISO 7064 MOD-97-10: move the first four characters to the end, turn each letter into its position in the alphabet plus nine, and read the result as one long number, which must leave remainder 1 when divided by 97. That catches every single-character mistake and almost every swap of two neighbouring characters, which is what it was designed for and why an IBAN is worth checking before you pay rather than after. What it cannot do is tell you the account exists, is open, or belongs to the person you think — a random string of the right shape passes about once in 97 tries, and no amount of arithmetic reaches into a bank. This page runs entirely in your browser, so the number you type is not sent anywhere.
How to use the Czechia IBAN Validator
- Paste the Czech IBAN — spaces and dashes are fine.
- Read the three checks: mod-97, length and structure.
- If it fails, the page says which check failed and what that usually means.
About the Czechia IBAN Validator
Checks a Czech IBAN three ways — checksum, length and structure — and says which of the three failed when one does, because they mean different things.
What people use it for
- Checking a Czech IBAN before sending money to it.
- Finding the bank code inside an IBAN you have been given.
- Confirming a Czech number was typed or pasted correctly.
Details
| Length | 24 characters, always |
|---|---|
| Structure | 4!n6!n10!n after the check digits |
| In words | CZ, 2 check digits, then 4 digits, then 6 digits, then 10 digits |
| Bank code | 4 characters — 0800 in the example |
| Example | CZ65 0800 0000 1920 0014 5399 |
| Check digits | Always between 02 and 98. 00, 01 and 99 cannot occur |
| Privacy | The arithmetic runs in your browser. Nothing you type is sent anywhere |
The maths behind it
This tool uses ISO 7064 MOD-97-10 — move the first four characters to the end, replace each letter with its position plus nine, and a valid IBAN leaves remainder 1 on division by 97. On top of that, Czech IBANs are exactly 24 characters and follow 4!n6!n10!n. Every intermediate value is shown on screen, so the result can be checked by hand.
Three checks, reported separately on purpose. A length error means a character is missing or extra, a structure error means a letter sits where a digit belongs, and a checksum failure with both of those right means a genuine typo inside the number — most often two neighbouring characters swapped.
Where this tool stops
It checks arithmetic and shape. It cannot tell you the account exists or who it belongs to, it does not look the bank up, and it does not verify any national check digits Czechia may use inside its own account number — those are separate rules, computed differently, and passing mod-97 says nothing about them.
Frequently asked questions
How many characters is a Czech IBAN?
Exactly 24, with no exceptions. After the two check digits the structure is 4!n6!n10!n — 4 digits, then 6 digits, then 10 digits. A number of any other length is not a Czech IBAN, whatever else about it looks right.
What is the six-digit part in the middle of a Czech IBAN?
The account prefix. Czech domestic accounts are written prefix-account/bank, and the prefix is often zeros — but when it is not, leaving it out changes the account entirely.
Where is the bank code in a Czech IBAN?
The 4 characters after the check digits are the bank code — 0800 in the example — and the remaining 16 are the account number, 0000192000145399.
Does a valid checksum mean the account exists?
No, and this is the thing worth taking away. Mod-97 proves the number is internally consistent — that it was probably typed correctly. It says nothing about whether the account is open, or whose it is. A random string of the right length passes about once in every 97 attempts. Only the bank can confirm the rest.
Is it safe to paste an IBAN here?
The checking happens in your browser and the number is never sent to a server — there is no request to make one. An IBAN is not a secret the way a card number is, since it is printed on every invoice you send, but it is still yours, and it does not leave your machine here.
Are there any usage caps on the Czechia IBAN Validator?
There is no cost and no cap. The Czechia IBAN Validator is not a demo of a paid product, so nothing is held back or watermarked.
Is my data uploaded anywhere?
No. The Czechia IBAN Validator runs entirely in your browser using JavaScript. Your input never reaches inputtesthub.com or any third party — open your browser's Network tab while you use it and you will see no request go out.
What formula does the Czechia IBAN Validator use?
It uses ISO 7064 MOD-97-10 — move the first four characters to the end, replace each letter with its position plus nine, and a valid IBAN leaves remainder 1 on division by 97. On top of that, Czech IBANs are exactly 24 characters and follow 4!n6!n10!n. The full working is printed under the result, so you can follow every step rather than trusting a black box.
What do people use the Czechia IBAN Validator for most?
Typical uses: checking a Czech IBAN before sending money to it. Finding the bank code inside an IBAN you have been given. Confirming a Czech number was typed or pasted correctly. It is built for exactly those cases rather than being a general-purpose tool with this bolted on.
What are the limits of the Czechia IBAN Validator?
It checks arithmetic and shape. It cannot tell you the account exists or who it belongs to, it does not look the bank up, and it does not verify any national check digits Czechia may use inside its own account number — those are separate rules, computed differently, and passing mod-97 says nothing about them. Knowing where a tool stops being trustworthy matters more than the cases where it works.
What are the reference figures here?
Length is 24 characters, always. Structure is 4!n6!n10!n after the check digits. In words is CZ, 2 check digits, then 4 digits, then 6 digits, then 10 digits. These are printed on the page itself, so you do not have to take them on trust.
Can I use the Czechia IBAN Validator on mobile?
Yes. The page is responsive and the utility 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.
Related security tools
All 10002
Hash Generator
Generates MD5, SHA-1, SHA-256, SHA-384 and SHA-512 hashes of any text, all at once.
03
MD5 Hash Generator
Generates an MD5 hash of any text or string, with optional HMAC and uppercase output.
04
SHA-256 Hash Generator
Generates SHA-256 hashes using the browser's Web Crypto API, with HMAC support.
05
SHA-1 Hash Generator
Generates SHA-1 hashes, still required by some legacy systems and Git object addressing.
06
SHA-512 Hash Generator
Generates SHA-512 hashes for checksums, signatures and archival fingerprints. Runs in your…
07
Base32 Encoder and Decoder
Encodes and decodes Base32, the alphabet used by TOTP secrets and some file systems.
08
Base58 Encoder and Decoder
Encodes and decodes Base58, the alphabet used by Bitcoin addresses and short identifiers.
09
AES Text Encryption
Encrypts and decrypts text with AES-GCM 256-bit using a password, entirely in your browser.
10
XOR Cipher Tool
Applies a repeating-key XOR to text or hex, the operation behind many simple obfuscation…