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United States SMS Best Practices, Compliance, and Features
United States SMS Market Overview
Locale name:
United States
ISO code:
US
Region
North America
Mobile country code (MCC)
310, 311
Dialing Code
+1
Market Conditions: The United States has one of the world's most mature SMS markets, dominated by major carriers including AT&T, Verizon, and T-Mobile. While OTT messaging apps like WhatsApp and Facebook Messenger are popular, SMS remains a critical communication channel with nearly universal reach. The market shows a relatively even split between Android (around 52%) and iOS (around 48%) users, with both platforms fully supporting standard SMS features.
Key SMS Features and Capabilities in United States
The United States offers comprehensive SMS capabilities including two-way messaging, concatenation, and MMS support, with strong carrier infrastructure and standardized delivery protocols.
Two-way SMS Support
The United States fully supports two-way SMS messaging across all major carriers. There are no specific restrictions beyond standard compliance requirements and proper registration for A2P (Application-to-Person) messaging through the 10DLC registration process.
Concatenated Messages (Segmented SMS)
Support: Yes, concatenation is fully supported across all major U.S. carriers. Message length rules: Messages can contain up to 1600 characters before splitting occurs. Single SMS messages are limited to 160 GSM-7 characters or 70 UCS-2 characters. Encoding considerations: GSM-7 encoding is used for standard ASCII characters, while UCS-2 encoding is automatically applied for messages containing special characters or Unicode, reducing the per-segment character limit from 160 to 70.
MMS Support
MMS is fully supported across all major U.S. carriers, allowing for rich media content including images, short videos, and audio clips. Best practices include keeping media files under 1MB and using common formats (JPEG, GIF, PNG for images; MP4 for video) to ensure broad compatibility.
Recipient Phone Number Compatibility
Number Portability
Number portability is available and widely implemented across all U.S. carriers. This allows users to keep their phone numbers when switching providers. While this doesn't directly affect SMS delivery, carriers maintain a central database to ensure proper message routing.
Sending SMS to Landlines
SMS to landline is possible but varies by carrier and landline provider. When attempted, some carriers will convert SMS messages to text-to-speech voice calls for landline recipients, while others may simply fail to deliver. It's recommended to verify number types before sending and filter out landline numbers from SMS campaigns.
Compliance and Regulatory Guidelines for SMS in United States
SMS marketing in the United States is primarily regulated by the Telephone Consumer Protection Act (TCPA), the CAN-SPAM Act, and Federal Communications Commission (FCC) guidelines. The CTIA (Cellular Telecommunications Industry Association) provides additional industry standards that should be followed. Companies must also comply with state-specific regulations and the A2P 10DLC registration requirements.
Consent and Opt-In
Explicit Written Consent Required: The TCPA mandates obtaining explicit written consent before sending marketing messages. This consent must be:
Clear and conspicuous
Specific to SMS marketing
Obtained through affirmative action (e.g., checking a box, sending a keyword)
Documented and stored for compliance
Best Practices for Obtaining Consent:
Use double opt-in verification
Clearly state message frequency and purpose
Maintain detailed consent records including timestamp, source, and opt-in method
Include clear terms and conditions during opt-in
HELP/STOP and Other Commands
Required Keywords:
STOP, UNSUBSCRIBE, CANCEL, END, QUIT for opt-out
HELP or INFO for program information
All keywords must be supported in both upper and lower case
Language Requirements:
Commands must work in English
If marketing in other languages, corresponding translations of commands must be supported
Initial confirmation message must include opt-out instructions
Do Not Call / Do Not Disturb Registries
The National Do Not Call Registry applies to SMS marketing. Businesses must:
Check the registry every 31 days
Remove registered numbers from marketing lists
Maintain internal do-not-contact lists
Honor opt-out requests within 24 hours
Keep records of opt-out requests for five years
Time Zone Sensitivity
Time Restrictions:
Avoid sending between 9 PM and 8 AM local recipient time
Consider stricter state-specific quiet hours
Emergency alerts may be exempt from time restrictions
Account for daylight saving time changes
Phone Numbers Options and SMS Sender Types for in United States
Alphanumeric Sender ID
Operator network capability: Not supported in the US market Registration requirements: N/A Sender ID preservation: N/A - Alphanumeric sender IDs are not displayed to US recipients
Long Codes (10DLC)
Domestic vs. International:
Domestic 10DLC numbers fully supported with proper registration
International long codes not supported for A2P messaging
Sender ID preservation: Yes, original number displayed to recipients Provisioning time: 1-3 business days after A2P 10DLC registration Use cases:
Two-factor authentication
Customer service
Appointment reminders
Transactional messages
Short Codes
Support: Fully supported across all major carriers Provisioning time: 8-12 weeks for approval and activation Use cases:
High-volume marketing campaigns
Time-sensitive alerts
Two-factor authentication
Customer loyalty programs
Restricted SMS Content, Industries, and Use Cases
Prohibited Content:
SHAFT (Sex, Hate, Alcohol, Firearms, Tobacco)
Illegal substances
Gambling without proper licensing
Loan advertisements from third-party lenders
Get-rich-quick schemes
Deceptive marketing practices
Content Filtering
Carrier Filtering Rules:
Messages are screened for prohibited content
Spam patterns trigger automatic blocking
URL shorteners may be flagged as suspicious
Tips to Avoid Blocking:
Use registered domains instead of shortened URLs
Avoid excessive punctuation and all-caps
Maintain consistent sending patterns
Include clear opt-out instructions
Use approved short codes or registered 10DLC numbers
Best Practices for Sending SMS in United States
Messaging Strategy
Keep messages under 160 characters when possible
Include clear call-to-action
Use personalization tokens thoughtfully
Maintain consistent brand voice
Include business name in each message
Sending Frequency and Timing
Limit to 2-4 messages per week maximum
Space messages evenly throughout the month
Respect quiet hours and time zones
Avoid major holidays unless relevant
Localization
Primary language is English
Consider Spanish for targeted demographics
Use clear, region-appropriate terminology
Avoid colloquialisms that may not translate well
Opt-Out Management
Process opt-outs in real-time
Send confirmation of opt-out
Maintain opt-out lists across all campaigns
Regular audit of opt-out compliance
Testing and Monitoring
Test across AT&T, Verizon, T-Mobile networks
Monitor delivery rates by carrier
Track opt-out rates and patterns
Regular testing of opt-out functionality
Monitor for carrier filtering changes
SMS API integrations for United States
Twilio
Twilio provides a robust SMS API with comprehensive documentation and strong support for US messaging requirements. Integration requires an Account SID and Auth Token from the Twilio Console.
import{ Twilio }from'twilio';// Initialize client with environment variablesconst client =newTwilio( process.env.TWILIO_ACCOUNT_SID!, process.env.TWILIO_AUTH_TOKEN!);asyncfunctionsendSMS(to:string, message:string){try{// Send message using registered 10DLC numberconst response =await client.messages.create({ body: message, to: to,// Must be in E.164 format: +1XXXXXXXXXX from: process.env.TWILIO_PHONE_NUMBER,// Optional: statusCallback URL for delivery updates statusCallback:'https://your-domain.com/webhook'});console.log(`Message sent successfully: ${response.sid}`);return response;}catch(error){console.error('Error sending message:', error);throw error;}}
Sinch
Sinch offers a straightforward REST API for SMS messaging with strong delivery rates in the US market. Authentication uses an API Token and Service Plan ID.