Email Validator: Format Checking for Single Addresses and Bulk Lists
Before you save an email to a database or trigger a signup flow, it's worth confirming the address is at least structurally valid. Our Email Validator checks an address against the practical rules that real mail servers enforce, shows you exactly which rule failed, and can validate an entire pasted list in one pass.
Local part ≤ 64 chars, full address ≤ 254 chars, domain must end in a valid TLD.
What 'Valid Format' Actually Means
Email format validation confirms the string is syntactically well-formed — it has a local part, an '@', and a domain with a valid top-level domain, with no illegal characters or malformed dots. It cannot confirm the mailbox exists, is spelled correctly, or accepts mail, since that requires actually contacting the recipient's mail server.
The Rules Behind the Checklist
This tool checks six practical rules pulled from RFC 5321/5322: overall length limits, local-part length, no consecutive or leading/trailing dots in the local part, and a domain ending in a proper top-level domain. These catch the overwhelming majority of malformed addresses without rejecting valid ones over obscure edge cases.
When to Use Bulk Validation
If you're cleaning a mailing list, an exported CRM report, or user-submitted CSV data, paste the whole list into the bulk validator. It flags every malformed line at once and lets you copy just the valid addresses forward, instead of checking each one manually.
Practical Examples
Catching a Typo'd Domain
A common real-world mistake.
- 1.Input: jane@gmial..com
- 2.Fails: No consecutive dots
- 3.Fix: jane@gmail.com
Cleaning an Exported List
Filtering a CSV export before an email campaign.
- 1.Paste 500 rows into Bulk Validation
- 2.Result: 487 valid, 13 invalid
- 3.Copy Valid button exports the clean list
What Gets Flagged
- Consecutive dots: john..doe@example.com
- Leading/trailing dot: .jane@example.com
- Missing TLD: user@localhost
- Local part over 64 characters
- Illegal characters outside the standard allowed set
This Tool Is Not a Substitute For
- Deliverability checks: Use an SMTP/MX-record verification service for that
- Disposable-email detection: Format-valid doesn't mean it's not a temp-mail address
- Confirming ownership: A verification email is still the only reliable proof
Frequently Asked Questions
Does this tool check if the email actually exists?
No. Format validation only confirms the string follows valid email syntax — it doesn't send any network request, so it can't confirm the mailbox exists or is currently active. That would require an SMTP handshake or a verification email.
What are the length limits it checks?
The local part (before the @) must be 64 characters or fewer, and the full address must be 254 characters or fewer, per RFC 5321.
Why did my email fail even though it looks fine?
Common causes are consecutive dots (john..doe@x.com), a local part starting or ending with a dot, or a domain missing a valid top-level domain (like .com or .org).
Can I validate a whole list of emails at once?
Yes. Paste one email per line into the bulk validator and it will check every line, then let you copy just the valid ones.
Does this support quoted or unusual local parts like "john doe"@example.com?
No. This validator targets the common, practical email format used by virtually all real-world addresses, not the full quoted-string edge cases in the RFC 5322 grammar.
Is my email data uploaded anywhere?
No. All validation happens locally in your browser using JavaScript regex and string checks — nothing is sent to a server, which matters if you're checking a real customer list.
Why is a two-letter TLD required?
Every registered top-level domain (like .com, .io, .co) is at least two letters, so a domain ending in a single character or no letters at all can't be a valid, deliverable address.