An email syntax validator checks whether an email address is correctly formatted according to RFC 5322 rules — verifying the local part, domain, TLD, and character constraints. Use it before sending mail, importing lists, or writing validation logic in your app.
Validation updates as you type — no button needed.
Validation Checks
Parsed Breakdown
Validation Rules (RFC 5322)
@ symbol: Exactly one @ is required. Multiple @ symbols or a missing @ are always invalid.
Local part (before @): 1–64 characters. Cannot start or end with a dot. No two consecutive dots. Characters allowed: A–Z, a–z, 0–9, and ! # $ % & ' * + - / = ? ^ _ ` { | } ~ and dots.
Domain (after @): Must contain at least one dot. Each label (segment between dots) must be 1–63 characters, contain only letters, digits, and hyphens, and cannot start or end with a hyphen.
TLD (last label): Must be 2 or more alphabetic characters only (e.g., .com, .io, .museum). Numeric TLDs are not valid.
Total length: The entire email address must not exceed 254 characters per RFC 5321.
Note: This tool validates syntax only. It does not verify that the email address exists or can receive mail.
How to Use the Email Syntax Validator
Email syntax errors are one of the most common causes of failed form submissions, bounced transactional emails, and broken import pipelines. An email address that looks right can still fail RFC 5322 validation — missing a TLD, having a double dot, or including a space. This email syntax validator checks every rule in real time as you type.
Step 1: Type or Paste Your Email Address
Enter the email address in the input field. Validation starts automatically after 300ms of idle typing — no button press needed. The tool checks whether the address is correctly structured per the simplified RFC 5322 rules used in practice.
Step 2: Review the Checklist
Below the input, you'll see a pass/fail checklist for each validation rule: whether the @ symbol is present and unique, whether the local part (the portion before @) follows length and character rules, whether the domain contains a dot and uses valid label characters, and whether the TLD is a valid alphabetic string of at least 2 characters. Each failing check is highlighted in red so you know exactly what's wrong.
Step 3: Check the Parsed Breakdown
When enough of the address is present to parse, the tool shows a breakdown: local part, domain, and TLD extracted separately. This is useful when debugging addresses that look correct but have subtle formatting issues — for example, an address like user@sub.domain.co.uk will show the full domain and extract uk as the TLD.
Common Email Validation Mistakes
The most frequent email syntax errors are: missing the @ symbol entirely, using two consecutive dots (user..name@example.com), leading or trailing dots in the local part (.user@example.com), numeric TLDs, and domain labels that start or end with a hyphen. This tool catches all of these cases and explains which specific rule failed.
Syntax Validation vs. Deliverability Check
A valid syntax does not guarantee that the email address exists or can receive mail. Syntax validation confirms the format; deliverability checking requires sending an email or querying the mail server's MX records via SMTP. Use this tool when you need to confirm an address is structurally correct — for example, before accepting a form submission, importing a contact list, or writing test data for an application.
FAQ
Is this email validator free?
Yes, completely free. No signup, no API key, no rate limits. All validation runs in your browser using JavaScript — no data is ever sent to a server.
Is my email address data safe?
Absolutely. This tool runs entirely in your browser. Your email address is never transmitted to any server, stored in any database, or shared with anyone. You can disconnect from the internet and the tool will still work.
Does this check if an email address actually exists?
No. This tool validates email syntax only — it checks whether the format is correct per RFC 5322 rules. To verify that an email address actually exists and can receive mail, you would need to send an actual email or use an SMTP verification service that connects to the mail server.
What makes an email address syntactically valid?
A valid email must have exactly one @ symbol, a local part (1-64 chars, no leading/trailing dots, no consecutive dots), a domain with at least one dot, domain labels of 1-63 alphanumeric or hyphen characters, and a TLD of 2+ alphabetic characters. The total length cannot exceed 254 characters.
Why does my email show as invalid even though it works?
This tool validates strict RFC 5322 syntax. Some email providers accept non-standard addresses that technically violate the spec. If your email works in practice, that's fine — real-world email servers often have more lenient rules than the formal standard.
Can I validate multiple email addresses at once?
This tool validates one email at a time for detailed per-check feedback. If you need to extract and check many emails from a block of text, try the Email Extractor tool in the same utilities category.