What is E.164?
E.164 is the international standard that formats a phone number as a leading plus sign followed by the country code and subscriber number, with a maximum of 15 digits — for example, +15551234567.
+1 555 123 4567
│ │ └──────── subscriber number
│ └──────────── area / national prefix
└─────────────── country code (1 = US/Canada)
# Stored and sent with no spaces or dashes:
+15551234567 # max 15 digits, always starts with +One canonical string per phone number — no ambiguity.
One number format, everywhere.
The VanceTel REST API accepts and returns phone numbers in E.164. Because every from and to is the same canonical string, contact matching and caller-ID resolution stay consistent between the API, the webhooks and the softphone inbox.
E.164 in practice.
A web form collects a number a visitor types as 555-123-4567. Before calling the API, the app normalizes it to +15551234567. That single canonical value is what VanceTel stores on the contact, sends the text to, and matches against the next inbound message — so the conversation always threads to the right person.
Keep reading.
E.164 questions.
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What is an example of an E.164 number?
A US number like (555) 123-4567 becomes +15551234567 in E.164: a plus sign, the country code 1, then the 10-digit national number, with no spaces, dashes or parentheses. The whole string is at most 15 digits after the plus.
Why does an SMS or voice API require E.164?
E.164 removes ambiguity. Because it carries the country code and uses one consistent shape, a platform can route a message or call internationally without guessing the locale. VanceTel expects from and to numbers in E.164 so every request resolves to exactly one phone number.
How does VanceTel use E.164?
You pass numbers in E.164 to the VanceTel REST API — for example "to": "+15557654321" — and webhook payloads return numbers the same way. Consistent formatting means caller-ID resolution and contact matching line up across the softphone and the API.