Twilio strongly encourages 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.
E.164 Phone Number Formatting
E.164 formatting for phone numbers entails the following:
- A + (plus) sign
- International Country Calling code
- Local Area code
- 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, 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, a great tool is the free online Twilio Lookup tool. This simple tool will help validate any phone number to make sure it is correctly formatted to send or receive calls. This service is also available via our API, with additional pay options for Caller ID and Provider lookup. Learn more about the Lookup API here.