Can you tell me if a number is on WhatsApp?

No, and neither can anyone else honestly. Registration cannot be checked from a browser, and checking it from a server breaks WhatsApp's terms. Any tool claiming to do it is guessing or scraping. What we check is the format, the country and the length — which is what actually causes most broken links.

Why is my landline reported as valid?

Because it is. WhatsApp Business accounts can be registered on a landline verified by a voice call, so refusing landlines would reject real customers. We show it as a note, never as a failure.

What happens to the numbers I paste?

Nothing leaves the page. The check runs in your browser, the downloads are generated there too, and no number appears in any analytics event or error report.

Number validator Free, no signup

Check the numbers before you message them

Paste one number or five thousand. You get the E.164 form, the country, and a specific reason for every row that fails — not the word “invalid”.

WhatsApp number validator

This checks the format, the country, the length and whether the number is a real, assignable range.

No tool can honestly tell you whether a number is registered on WhatsApp. That cannot be checked from a browser, and checking it from a server breaks WhatsApp's terms.

Five made-up numbers, two rejected on purpose. Your own list replaces it.

Country for numbers with no + prefix

Rows that already start with + or 00 are read as written and are never rewritten.

Numbers, one per line

One number per line. A label before a comma, tab or semicolon is kept. Up to 5000 rows.

First line is a headerFlag duplicates

Result

Paste some numbers to check them.

Free WhatsApp button for your site

Stop losing conversions. Your customers are already on WhatsApp.

Every visitor who leaves without messaging you is a sale that never happened. Put a WhatsApp button on your site with a single line of code, and let them start the chat in one tap — from any page, on any device.

Get my free button

Free forever · No credit card · Live in minutes

What you actually get

A reason you can act on

“Wrong length for +34: got 8, expected 9” tells you what to fix. “Invalid” does not, and it is what every other tool returns.

Duplicates found across spellings

+44 20 7946 0123 and 00442079460123 are one customer. Matching on the parsed number rather than the text is what stops you messaging them twice.

Your list never leaves your browser

A customer list is the most sensitive thing you can paste into a web page. This one is parsed on your own device — there is no upload and no server to leak.

Common questions

Can you tell me if a number is on WhatsApp?: No, and neither can anyone else honestly. Registration cannot be checked from a browser, and checking it from a server breaks WhatsApp's terms. Any tool claiming to do it is guessing or scraping. What we check is the format, the country and the length — which is what actually causes most broken links.
Why is my landline reported as valid?: Because it is. WhatsApp Business accounts can be registered on a landline verified by a voice call, so refusing landlines would reject real customers. We show it as a note, never as a failure.
What happens to the numbers I paste?: Nothing leaves the page. The check runs in your browser, the downloads are generated there too, and no number appears in any analytics event or error report.