Email Validator
Check whether an email address is syntactically valid, see exactly what's wrong, and get a suggested fix for common typos. Runs entirely in your browser — no server, no DNS lookup, no sign-up.
What this tool does
The Email Validator checks whether an email address is syntactically valid and tells you exactly what is wrong when it isn't. It runs entirely in your browser: nothing is sent to a server, it works offline, and there is no sign-up. It is also syntax-only — it never performs a DNS, MX, or SMTP lookup, so it confirms the address is well-formed, not that the mailbox actually exists.
Paste an address (a Name <addr> or mailto:addr wrapper is unwrapped
automatically) and it reports whether the address is valid, the local part and
domain it parsed, every hard error, every soft warning, and — when it spots a
likely typo — a suggested correction.
What it checks
| Check | Example caught |
|---|---|
Missing or duplicated @ | userexample.com, a@[email protected] |
| Empty or over-long parts | @example.com, a local part over 64 characters |
| Leading / trailing / consecutive dots | [email protected], [email protected], [email protected] |
| Illegal characters | a space, _ in the domain, non-ASCII without IDN |
| Bad domain | no dot (user@localhost), a label edge hyphen, an empty label |
| Misspelled provider | [email protected] → suggests [email protected] |
| Misspelled TLD | [email protected] → suggests [email protected] |
| Suspicious TLD | an all-numeric top-level domain |
| Formatting noise | surrounding whitespace, a quoted local part, an IP-address literal |
Valid vs. warning
A result is marked Valid: yes when there are no hard syntax errors. It can
still carry warnings — for example [email protected] is perfectly well-formed,
but gmial.com is almost certainly a typo for gmail.com, so the tool flags it
and offers the corrected address as a suggestion. Warnings never make an address
invalid; they just point out things worth a second look before you hit send.
Why validate format only?
Real-time DNS/MX or SMTP verification requires a network round-trip to the
recipient's mail server, which is slow, often rate-limited, and frequently
blocked by anti-abuse measures. Catching the obvious syntax mistakes and typos
before you send — instantly and privately, right in the browser — fixes the
large majority of bad addresses (fat-fingered domains, stray spaces, missing
@) without ever leaking the address to a third-party service.
FAQ
Does "Valid: yes" mean the mailbox actually exists?
No. The check is syntax-only — it confirms the address is well-formed under RFC 5321/5322 rules. It never performs a DNS, MX, or SMTP lookup, so a valid result can still bounce if the mailbox was deleted or never existed.
What length limits does it enforce?
The RFC limits: 254 characters for the whole address, 64 for the local part
(before the @), 253 for the domain, and 63 per domain label. Anything longer
is reported as a hard error with the offending length.
Can I paste "Jane Doe <[email protected]>" or a mailto: link?
Yes — a Name <addr> display form, bare angle brackets, or a mailto: prefix
is stripped automatically before validation, so you can paste straight from an
email header or a web link.
Why is user@localhost marked invalid?
The domain must contain at least one dot. Single-label domains like
localhost work on private networks but aren't routable internet addresses,
so the tool treats a dotless domain as a hard error.
Developer & Automation Access
Run it from the terminal
Same engine as this page, headless — via the gizza CLI:
gizza tool email-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/email-validator/?input=user%40gmial.comMachine-readable descriptor: tool.json — title + parameters JSON Schema for agents.