Email Format Check
Email Format Check — runs in your browser. Inputs are not stored.
Email format check
Enter values, then press Calculate.
Checks regex format only. Does not verify MX records or whether the address exists.
How to use
- Enter addresses in email (one per line, or comma/space separated). Semicolons are also delimiters.
- You can paste several at once; they are split on spaces, commas, and semicolons.
- Press Check to see valid and invalid counts in the stats.
- Result lists each address as OK or NG, a tab, and the original on its own line.
- Reset clears input and hides the result area. There is no copy button.
Key concepts
Email format check only tests whether a string matches a common address pattern and length limits. The local part may include dots and some special characters; the domain should look like labels plus dots. If the overall length is too long, it is invalid even if the pattern matches. MX records, mailbox existence, and deliverability are not checked. Use it to catch typos before a signup form. Multiple lines are split by delimiters and counted as valid vs invalid, which helps clean a list.
IDN domains and quoted local parts can fail. Addresses are not sent to a server for verification and DNS is not queried. Paste a bulk list to split valid/invalid at a glance, then paste result lines into a sheet and fix bad rows. Real sendability still needs a mail server. An empty field plus Check only shows “please enter an email” and counts stay 0.
Example
Checking [email protected] and bad@@test separated by a comma yields valid 1, invalid 1, and two result lines: OK plus the good address, NG plus the bad one. An empty field shows only the enter-an-email prompt.
Related: Character counter · JSON formatter · HTML validator
Frequently asked questions
Does email format check mean the address exists?
Existence is not checked. Only regex form and length are tested—no MX record or deliverability lookup.
How do I enter several addresses?
One per line, or separate with commas, spaces, or semicolons. Empty tokens are skipped.
What are OK and NG in the result?
OK passed the pattern and length limits; NG failed. Order is status, tab, then original.
What happens to a very long address?
Even if the pattern matches, exceeding the overall length limit counts as invalid NG.
Is the email list sent to a server?
No. Regex matching runs only in the browser, and there is no DNS lookup.
Is there a copy button?
No. Select the OK/NG lines in the result box to copy. Reset hides the stats area.
Last reviewed: 2026-09-04