United States (+1) Country Calling Code & SMS Guide
Complete engineering reference for phone numbering formats, domestic trunk prefixes, cellular mobile operator allocations, and regulatory A2P SMS requirements in United States.
Telephony Architecture & Carrier Allocations
A2P Messaging Regulations & Firewall Policies
Mandatory 10DLC campaign vetting via The Campaign Registry (TCR). Unregistered traffic is subject to severe carrier filtering and per-message surcharges ($0.015+).
Unsupported on standard peer-to-peer or 10DLC routes. Carrier aggregators overwrite alphanumeric headers with dedicated shortcodes or pooled long codes.
Fully supported on 10DLC local numbers and verified Toll-Free SMS routes.
GSM-7 standard (160 characters/segment). UCS-2 (70 characters/segment) activated on emojis or non-GSM characters.
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Check if a United States phone number conforms to the national numbering plan, classify mobile vs VoIP allocation, and obtain canonical E.164 standardization.
Frequently Asked Questions for United States
What is the official international dialing code for the United States?
The international country calling code for the United States is +1, established under the North American Numbering Plan (NANPA).
Are Alphanumeric Sender IDs supported for SMS in the United States?
No. Major US carriers (AT&T, Verizon, T-Mobile) do not support Alphanumeric Sender IDs. All commercial A2P messaging must originate from a registered 10DLC number, shortcode, or verified Toll-Free number.
What are the registration requirements for sending A2P SMS in the US?
Under US 10DLC regulations, businesses must register their Brand (EIN/Tax ID) and specific messaging Campaigns through The Campaign Registry (TCR) before sending commercial traffic.
How are US phone numbers formatted in E.164?
US numbers in E.164 format start with +1 followed by the 3-digit Area Code (NPA) and 7-digit subscriber number (NXX-XXXX), e.g., +14155552671.