Formatting International Phone Numbers

Twilio strongly encourages using E.164 phone number formatting for all phone numbers both in the ‘To’ and ‘From’ fields. This is an internationally-recognized standard phone number format that will help to ensure deliverability of calls and SMS messages across the globe.

Instead of reaching out from Twilio using an International Call Prefix like 011, simply use an E.164 formatted phone number.

Notice: Short Code messaging numbers do not require a plus sign or country code. For more information, please see Formatting Short Code Numbers.

E.164 Phone Number Formatting

E.164 formatting for phone numbers entails the following:

  1. A + (plus) sign
  2. International Country Calling code
  3. Local Area code
  4. Local Phone number

For example, here’s a US-based number in standard local formatting: (415) 555-2671


Here’s the same phone number in E.164 formatting: +14155552671


In the UK, and many other countries internationally, local dialing may require the addition of a '0' in front of the subscriber number. With E.164 formatting, this '0' must usually be removed.

For example, here’s a UK-based number in standard local formatting: 020 7183 8750


Here’s the same phone number in E.164 formatting: +442071838750


Help with E.164 Formatting

If you are unsure of the correct country code for a number, a good reference is this Wikipedia page that lists countries and their calling codes.

If you need additional help determining the correct E.164 formatting for a phone number, consider using Twilio Lookup. The Lookup API can help validate any phone number to make sure it is correctly formatted to send or receive calls. Lookup also offers additional options for Caller ID and Provider lookup. Learn more about the Lookup API here.

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