Email Format Validator
Quick shape check + local/domain/TLD breakdown.
Overview
The Email Format Validator does a quick shape check on any email address and breaks it down into local part, domain and top-level domain. It does not send mail or query DNS — it answers the simpler question "is this string a syntactically plausible email address?" so you can flag obvious typos and weed out junk before any expensive verification step runs.
The validator is aimed at developers cleaning up sign-up forms, marketers scrubbing CSV lists before import and support agents spotting suspicious addresses in tickets. Long-tail searches like "is this email address syntactically valid", "extract domain from email string" and "fast email format check without DNS" all map here.
How it works
The tool implements the practical subset of RFC 5321 and RFC 5322 used by mainstream mail providers. It splits on the last unquoted @, then validates the local part (printable ASCII, dot-separated atoms, no leading/trailing dot) and the domain part (DNS labels of 1-63 characters, alphanumerics with hyphens, joined by dots, total length below 253). The TLD is extracted as the final label and checked against a permissive shape rather than a fixed allow-list, so newer TLDs like .dev and .coffee pass.
Beyond pass/fail, the validator returns the parsed local, domain and TLD so you can pivot on them — for example, blocking disposable-mail TLDs in a sign-up flow or grouping addresses by domain. Quoted-string local parts and IP-literal domains (user@[192.0.2.1]) are accepted but flagged because most consumer providers reject them.
Examples
ada@example.com → valid · local=ada · domain=example.com · tld=com
ada.lovelace+notes@analytics.io → valid · local=ada.lovelace+notes · tld=io
bad..dots@example.com → invalid (consecutive dots in local part)
user@[192.0.2.1] → valid (IP literal) · flagged as uncommon
FAQ
Does it verify the mailbox exists?
No. That requires an SMTP probe or a third-party verification API. The tool only checks syntax, which catches a large share of real-world typos for free.
Why are plus-tags allowed?
name+tag@domain.com is valid per RFC 5322 and supported by Gmail, FastMail and most modern providers. Many users rely on it for filtering, so the validator does not strip or block them.
Does it check the TLD against ICANN?
It checks the TLD has the right shape (alphabetic, 2-63 characters) but does not maintain a live ICANN list, which would require constant updates.
Are international (UTF-8) addresses supported?
Punycoded domains pass. Raw Unicode local parts are accepted with a warning because many SMTP servers still reject SMTPUTF8.
Can I batch-validate a list?
Paste one address per line and the tool reports valid and invalid counts plus the parsed components for each row.