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Email syntax checker
See exactly which syntax rule an email address breaks, with a hint for common domain typos. Nothing leaves your browser.
Runs in your browser: nothing is sent anywhere. Results update as you type.
Email address syntax rules
An email address is local-part@domain.
- Local part: 1 to 64 characters. Letters, digits and the special characters
! # $ % & ' * + - / = ? ^ _ ` { | } ~. Dots are allowed, but not at the start, at the end or twice in a row. Quoted local parts ("john doe"@example.com) are technically valid but rarely accepted. - Domain: labels of letters, digits and hyphens, separated by dots, each up to 63 characters. A label cannot start or end with a hyphen. The top-level domain is letters only.
- Total length: at most 254 characters.
- Case: domains are case-insensitive; in practice, local parts are too.
The guide to the email address format explains each rule, with 25 valid and invalid examples.
Common mistakes
| Address | Problem |
|---|---|
john.doe@gmail | No top-level domain |
john..doe@ | Two dots in a row |
.john@gmail.com | Starts with a dot |
john doe@gmail.com | Space in the address |
john@gmial.com | Valid format, but a typo of gmail.com |
Frequently asked questions
What characters are allowed in an email address?
The local part (before the @) may contain letters, digits and ! # $ % & ' * + - / = ? ^ _ ` { | } ~ and dots, as long as dots are not first, last or doubled. The domain may contain letters, digits, hyphens and dots.
How long can an email address be?
The local part may have up to 64 characters and the whole address up to 254 characters.
Is valid syntax enough?
No. j7fq2@gmail.com is perfectly formatted but probably does not exist. Use the email validator to check the mailbox.
What is the best regex for email validation?
There is no perfect one. A practical pattern is
^[^\s@]+@[^\s@]+\.[^\s@]{2,}$ for instant form feedback; then validate the address properly on the server. Tested regex patterns for each programming language are in our email regex guide.Email validation API
Validate emails in your app
emailvalidation.io checks syntax, MX records and the mailbox over SMTP, flags disposable, role and free addresses and returns a quality score, in one request.
/v1/info Email validation API Read the documentation
100 free validations every month. No credit card required.
GET https://api.emailvalidation.io/v1/info?
{
"email": "support@emailvalidation.io",
"user": "support",
"tag": "",
"domain": "emailvalidation.io",
"format_valid": true,
"mx_found": true,
"smtp_check": true,
"catch_all": null,
"role": true,
"disposable": false,
"free": false,
"score": 0.64,
"state": "deliverable",
"reason": "low_quality",
"did_you_mean": "",
"catch_all_resolution": null,
"bounce_probability": null,
"status": "valid",
"sub_status": "role_based",
"explanation": "The mailbox exists, but it is a role address (such as info@ or support@), usually read by a team rather than one person.",
"recommended_action": "send_with_caution"
}Free email tools
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