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Format Validator

Validate emails, UUIDs, IP addresses, credit card numbers, IBANs and semver strings.

To validate a format, paste the value and choose what it should be. The tool checks emails, UUIDs, IPv4 and IPv6 addresses, credit card numbers via the Luhn algorithm, semantic versions, hex colours and URL slugs, explaining exactly which rule failed.

Runs in your browser
Privacy
Runs entirely in your browser — nothing is uploaded
Cost
Free, unlimited, no sign-up

Frequently asked questions

Why does my valid email fail some validators?

Because most validators implement a simplified rule rather than RFC 5322, which permits quoted strings, comments and characters almost nobody uses. Rejecting a technically valid address is common; the practical answer is to validate loosely and confirm by sending a message.

Can validation prove data is correct?

Only that it is well formed. A correctly structured IBAN with a valid check digit can still belong to no account, and a syntactically perfect email can bounce. Format checks catch typos, not falsehoods.

How to use the format validator

  1. 1Enter or paste your value to validate.
  2. 2Choose the validate as.
  3. 3The result appears immediately — copy or download it.

Embed this tool

Put the working format validator on your own site. It runs in your visitors' browsers exactly as it does here — free, no account, nothing uploaded.

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