E.164 Phone Number Format

E.164 exists so that a phone number stored once works everywhere. +14155550132 dials correctly from any phone, in any country, and matches exactly in any database — there is exactly one way to write each number.

Virtually every communications API standardizes on E.164: Twilio, WhatsApp Business, Vonage, AWS SNS, Firebase Auth, and SMS gateways all reject or misroute numbers that are not in this form. CRMs like Salesforce and HubSpot deduplicate contacts far more reliably when numbers are normalized to E.164 first.

E.164 Syntax Rules

• Starts with + followed by the country calling code (1–3 digits).
• Maximum 15 digits total (excluding the +).
• No spaces, hyphens, parentheses, dots or letters — digits only.
• National trunk prefixes (like the UK or German leading 0) are removed.
• Example: UK national 07400 123456 → E.164 +447400123456.

E.164 Numbers Around the World

The same numbers from our country guides, written in E.164 format:

Where E.164 Is Required

• Storing phone numbers in any database or CRM (one canonical form prevents duplicates).
• Sending SMS or WhatsApp messages through APIs like Twilio or Vonage.
• User sign-up and OTP verification flows (Firebase, Auth0).
• Syncing contacts between systems or running deduplication jobs.

Converting to E.164 in Code

import { parsePhoneNumber } from 'libphonenumber-js';

const phone = parsePhoneNumber('020 7946 0958', 'GB');
phone.format('E.164'); // '+442079460958'

import phonenumbers

n = phonenumbers.parse("020 7946 0958", "GB")
phonenumbers.format_number(n, phonenumbers.PhoneNumberFormat.E164)
# '+442079460958'

^\+[1-9]\d{1,14}$
// Checks E.164 shape — NOT whether the number actually exists.
// Use libphonenumber for real validation.

E.164: Developer Questions

Other Formats