What is E.164 phone format?
E.164 is the ITU-T standard that defines how phone numbers should be formatted to be universally routable. The format is a plus sign, a country code, and the national number, with no spaces, no dashes, no parentheses. "+14155550100", not "(415) 555-0100".
The rules
An E.164 number has a country calling code and national number, with at most 15 digits. APIs commonly write it with a leading plus sign. Use country-aware parsing instead of removing leading zeros indiscriminately; national numbering rules differ.
Examples
+14155550100 (United States). +442071234567 (United Kingdom). +81312345678 (Japan). +5511987654321 (Brazil). The country code can be one to three digits; the rest is country-specific. Most national numbers are seven to ten digits.
Why E.164 for storage
Use a normalized international number for supported phone and messaging API fields, and format it separately for display. Validate the destination using its country context. Check the endpoint schema: a display label, extension or short code is not interchangeable with an E.164 phone number.
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