What is E.164 format?

E.164 is the international standard for phone numbers: a leading + followed by the country code and national number, written as digits only and limited to 15 digits total.

Does my phone number leave my browser?

No. Formatting and validation run entirely in your browser. Nothing you type is sent to a server, logged, or stored.

Why do I need to pick a country?

A local number without a leading + does not identify its country. The selected country supplies the dialing code and national numbering rules.

How do I convert a UK phone number to E.164?

Choose United Kingdom, enter the local number, and use the result with +44 instead of the leading 0. For example, 07911 123456 becomes +447911123456.

What format do Twilio and WhatsApp expect?

They expect a plus sign, country code, and subscriber number without spaces or punctuation, such as +14155552671.

What does “possible but not confirmed valid” mean?

The length and structure are plausible, but this browser-only tool cannot confirm that the number is active or assigned.

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Built by UnifyPort

E.164 Phone Number Formatter

Normalize UK, WhatsApp, Twilio, and international phone numbers to E.164 — entirely in your browser.

Phone number

Default country

Used only when the number does not include a country code (no leading “+”).

Enter a phone number to get started

Why E.164?

E.164 is the international standard for phone numbers: a leading + followed by up to 15 digits, country code first, with no separators. Messaging APIs such as Twilio, WhatsApp, Telegram, and X expect this format. Normalizing once on input helps prevent delivery failures caused by missing country codes, parentheses, spaces, or leading zeros.

UK, Twilio, and WhatsApp examples

For a UK phone number, replace the trunk prefix 0 with country code +44: 07911 123456 becomes +447911123456. Twilio and WhatsApp use the same E.164 shape.

Before a production integration calls Send text message, use this formatter so your backend stores one canonical recipient identifier per contact.

FAQ

What is E.164 format?: E.164 is the international standard for phone numbers: a leading + followed by the country code and national number, written as digits only and limited to 15 digits total.
Does my phone number leave my browser?: No. Formatting and validation run entirely in your browser. Nothing you type is sent to a server, logged, or stored.
Why do I need to pick a country?: A local number without a leading + does not identify its country. The selected country supplies the dialing code and national numbering rules.
How do I convert a UK phone number to E.164?: Choose United Kingdom, enter the local number, and use the result with +44 instead of the leading 0. For example, 07911 123456 becomes +447911123456.
What format do Twilio and WhatsApp expect?: They expect a plus sign, country code, and subscriber number without spaces or punctuation, such as +14155552671.
What does “possible but not confirmed valid” mean?: The length and structure are plausible, but this browser-only tool cannot confirm that the number is active or assigned.