Format Validator
Check whether one value is a valid email, URL, IPv4/IPv6 address, phone number, or credit-card number. Auto-detect the format or validate a specific one — all locally, with no network lookups.
What this tool does
Paste one value and validate it as an email address, URL, IPv4/IPv6 address, phone number, or credit-card number. Leave the format on auto to try every supported check and report the detected format, or choose a specific format when you need a strict yes/no answer.
Everything runs locally in your browser. The checks are syntax and checksum checks only: there are no DNS, MX, reachability, carrier, or payment-network lookups.
Supported checks
- Email — common internet email syntax: one
@, sane local part, domain labels, and alphabetic top-level domain. It does not verify mailbox existence. - URL — requires a scheme such as
https://and a host; reports the scheme and host that were parsed. - IPv4 / IPv6 / IP — uses strict address parsing for either address family.
- Phone — allows a leading
+, spaces, hyphens, dots, and parentheses; must contain 7 to 15 digits. - Credit card — accepts spaces or hyphens, checks 12 to 19 digits with the Luhn algorithm, and reports a best-effort card brand.
Example
Input:
4111 1111 1111 1111
Format: credit-card
Output:
Input: 4111 1111 1111 1111
Format: credit-card
Valid: yes
Detail: valid card number; Luhn OK; brand Visa; 16 digits
Limits and edge cases
- This is a format validator, not an identity or availability check.
- Email validation intentionally does not perform DNS or MX lookups.
- URL validation requires
scheme://host; a bareexample.comis not treated as a valid URL. - Phone validation is length and character based; it does not know national numbering plans.
- Test card numbers such as
4111 1111 1111 1111can pass Luhn without being a real card.
FAQ
Does this verify that an email inbox or URL actually exists?
No. It checks syntax only. There are no DNS, MX, HTTP, or reachability probes, so private data stays local and the result does not depend on network access.
Why does a bare domain fail URL validation?
The URL check expects a full URL with a scheme and host, such as
https://example.com. A bare example.com can be a domain name, but it is not a
complete URL for this validator.
What does auto-detect do?
Auto-detect runs every supported check and reports the first valid match in a stable priority order: IPv4, IPv6, email, URL, credit card, then phone. It also prints a per-format pass/fail table so you can see ambiguous cases.
Is the credit-card check safe to use?
It performs only a local Luhn checksum and simple brand detection from the number prefix and length. It does not contact a bank or payment network, and a Luhn-pass number is not proof that a card exists or can be charged.
Developer & Automation Access
Run it from the terminal
Same engine as this page, headless — via the gizza CLI:
gizza tool format-validator "[email protected]"New to the CLI? Get gizza →
Open it by URL
Pre-fill and auto-run this tool with query parameters — the names match the API/CLI:
https://gizza.ai/tools/format-validator/?input=user%40example.com&format=auto&output=textMachine-readable descriptor: tool.json — title + parameters JSON Schema for agents.