E.164: definition and how it works
Published and updated
E.164 is the ITU standard for international phone numbers: a plus sign, the country code, and the national number with no spaces or punctuation, at most fifteen digits.
How it works
The International Telecommunication Union's Recommendation E.164, The international public telecommunication numbering plan, defines how a phone number is written so that it is unambiguous anywhere in the world. A number in E.164 form starts with a plus sign, continues with the one to three digit country code, and ends with the national significant number. There are no spaces, brackets, hyphens or trunk prefixes, and the whole thing is at most fifteen digits. A United States number reads +12015550123; a British mobile reads +447700900123.
SMS APIs require E.164 because a national number means different things in different countries. 07700 900123 is a mobile in the United Kingdom and nonsense in the United States. The leading zero is a trunk prefix used inside the country and must be dropped, which is the most common conversion mistake. Italy is the famous exception where the zero is part of the number for landlines.
Converting user input reliably needs a library, not a regular expression. Libraries built on the Google phone number metadata parse a number given a default country, strip formatting, drop the trunk prefix, validate the length and type, and output E.164. They also tell you whether a number is mobile, which matters because SMS to a landline fails silently on many routes.
Store numbers in E.164 and format them for display only when showing them to people.
- ITU-T Recommendation E.164, The international public telecommunication numbering plan, current edition 02/2026, in force. itu.int, checked on September 5, 2026
How this applies with textbee
POST /gateway/send-sms takes recipients in E.164, and the phone dials exactly what you pass. The phone number formatter tool converts a national number for any country the SIM might be in, and the country pages show the local shape.
Related terms
- SMS API: An SMS API is a programmatic interface, almost always HTTP, that lets software send text messages, read the ones that arrive, and check what happened to each one.
- Long code: A long code is a standard full-length phone number, such as a ten-digit United States number, used as the sender of SMS.
- Sender ID: The sender ID is what the recipient sees in the from field of a text message: a phone number, a short code, or a registered brand name.
Sources
- E.164, itu.int, checked on September 5, 2026