Email Validator
Check whether an email address is correctly formatted.
Runs in your browser Your input never leaves your device.
Report a problem with this tool
About this tool
Paste one email address per line and the tool marks each as valid or invalid format as you type. It checks the structure only: allowed characters before the @, a domain made of labels separated by dots, and label length limits. It does not look up DNS records, contact a mail server or confirm that the mailbox exists, so a well-formed address can still bounce. Everything runs in your browser and nothing you paste is sent to our servers. Use it to clean up a list before an import or to spot typos such as a missing dot or a double @.
How to use it
- Paste or type your addresses, one per line.
- Read the result for each line: a check mark means valid format, a cross means invalid.
- Fix the flagged lines and check again.
- Copy the result if you need it elsewhere.
Example
The domain needs at least one dot, so single-label hosts like localhost fail.
[email protected] ada@@example.com ada@localhost
✓ [email protected] — valid ✗ ada@@example.com — invalid format ✗ ada@localhost — invalid format
Format validation vs mailbox verification
Email validation can mean three different checks. This tool does the first one only.
A paid verification service usually adds the other two. You can do them yourself with the tools listed below, and the only proof that a person reads the inbox is a confirmation email they act on.
- Syntax
- Is the address built correctly: a local part, one @, and a domain with at least one dot. This page checks this.
- Domain
- Does the domain publish MX records, so it can receive mail at all. Use the MX Lookup tool for this.
- Mailbox
- Does the mail server accept the address. Many servers accept every address or block such probes, so this check is often inconclusive.
What the checker accepts
- Local part (before the @)
- Letters, digits and the symbols . ! # $ % & ' * + / = ? ^ _ ` { | } ~ -. Up to 64 characters. It cannot start with a dot, end with a dot or contain two dots in a row.
- Domain (after the @)
- Labels of letters, digits and hyphens separated by dots. Each label is 1 to 63 characters and cannot start or end with a hyphen. At least two labels are required.
- Not accepted
- Quoted local parts such as "john doe"@example.com, IP address domains in brackets, and non-ASCII letters. These are allowed by the standards but rare, and many sign-up forms reject them too.
Cleaning a list before an import
- Paste the column of addresses, one per line.
- Fix or remove every line marked invalid. Common causes are a missing dot in the domain, a trailing dot, a comma instead of a dot, or two @ signs.
- Check the remaining domains with MX Lookup if the list is old or typed by hand.
- Run the list through the Disposable Email Detector if throwaway sign-ups are a problem.
Common problems
- A valid-looking address still bounces
- Format checks cannot tell whether the mailbox exists. Send a confirmation email to verify it.
- An address with non-English letters is marked invalid
- Only ASCII letters, digits and the usual symbols are accepted, so internationalized addresses are reported as invalid format.
- Spaces or commas break a line
- Put exactly one address on each line. Surrounding spaces are trimmed, but spaces inside an address make it invalid.
Frequently asked questions
Can this tell me if an email address really exists?
No. It checks the format only. It makes no network request, so it cannot see whether the domain or the mailbox exists. Send a confirmation email to be sure.
Is a plus address like [email protected] valid?
Yes. The plus sign is allowed in the local part, and the checker accepts it. Whether the mail server delivers plus addresses depends on the provider.
Are uppercase letters a problem?
No. Uppercase letters pass the check. Domains are not case-sensitive, and most providers treat the local part as case-insensitive too, though the standard allows a server to tell them apart.