BrowserTools

Email Validator

Syntax and format checks, explained

By Guga — BrowserTools maintainer, Tbilisi, Georgia Updated 2026-09-04
Free Private No uploads
What is Email Validator?

Paste one address per line, or separate them with commas and semicolons, and each is taken apart and inspected. The local part is checked against its 64-character limit, a leading or trailing dot, consecutive dots, and characters outside the set the specification permits. The domain is checked for its 253-character limit, a missing dot, a top-level label under two characters, empty labels produced by a double dot, leading or trailing hyphens, and characters that are not letters, digits or hyphens. Twenty disposable providers — mailinator.com, guerrillamail.com, yopmail.com and similar — are flagged on their own, as is a domain written as a literal IP address. Every finding is labelled an error, a warning or a note, and only errors turn the verdict red. A running count tracks how many of the batch passed. It all happens in the page.

Validate email addresses with strict RFC-style syntax checks, plus domain, TLD and disposable-provider detection with human-readable explanations for every verdict.

Private Email Validator In Your Browser

Email Validator is processed locally with client-side JavaScript. Your files never touch a server, and there is no queue to wait in.

Step-by-Step

How to use Email Validator

1

Paste addresses into the text area, one per line or separated by commas, semicolons or spaces; up to 100 are read.

2

Read the Results panel, where every address gets a valid or invalid badge plus the findings it triggered.

3

Read severity from the dot colour: red marks hard errors, yellow marks warnings that may still be accepted, blue marks notes.

4

Watch the valid count beside the buttons to see how many of the batch passed without scrolling the list.

Key Capabilities
  • Input is split on whitespace, commas and semicolons, so a CSV column and a hand-typed list both work without reformatting.
  • Up to 100 addresses are processed per paste and each gets its own card, rather than stopping at the first problem.
  • Twenty known disposable providers are matched on the domain and reported as a warning rather than a syntax error.
  • Findings carry three severities — error, warning and note — and only an error changes the valid or invalid verdict.
Common Use Cases
  • A backend developer screens a pasted CSV column of signups and isolates the rows that would bounce before importing.
  • A QA engineer writes form-validation cases straight from the messages, such as a leading dot or a missing top-level domain.
  • Someone tidying an old mailing list strips out throwaway providers that were inflating the bounce rate on a campaign.
Clear Answers

Frequently Asked Questions

Does a valid verdict mean the mailbox exists?
No. This is a shape and syntax check performed in the page, and it cannot open a connection to the destination mail server. Establishing that a mailbox exists requires an SMTP conversation, which a browser cannot conduct and which many providers deliberately make awkward.
So what should run before a signup form?
This as the first filter, and a confirmation email as the real test. Send a token and refuse the account until it comes back — that is the only dependable way to know an address both accepts mail and belongs to whoever typed it.
Why is an unusual character only a warning?
Because the set the specification allows is wider than what mail servers actually implement. A local part holding a character outside the common set may be accepted by one provider and rejected by another, so it is reported without failing the address outright.
Are addresses with subdomains handled?
Yes, because every label between the dots is examined separately, so [email protected] is accepted. A hyphen at either end of any single label is still an error, even when the address as a whole looks entirely reasonable.