When to use short codes
- Good fit
- Consider alternatives
- High-volume alerts: Time-sensitive notifications to large audiences
- Two-factor authentication: OTP delivery at scale with high deliverability
- Marketing campaigns: Promotional messages with keyword opt-in (e.g., “Text JOIN to 12345”)
- Voting and polling: Interactive SMS campaigns
- Emergency notifications: Critical alerts requiring maximum throughput
Short code vs. other sender types
Provisioning process
1
Request a short code
Navigate to Short Code in Mission Control and submit your request.Choose your type:
Vanity codes are subject to availability. Request early — popular combinations may already be taken.
2
Complete your application
Provide details about your messaging program:
- Company information — Legal name, address, contact
- Use case description — What messages you’ll send
- Message content samples — Representative examples
- Volume estimates — Expected daily/monthly message volume
- Opt-in flow — How users subscribe (web form, keyword, etc.)
- Opt-out handling — STOP keyword support
- Help response — HELP keyword response content
3
Carrier certification
Your application is submitted to each major US carrier for review and approval:
4
Start messaging
Once approved by all target carriers, your short code appears under your messaging profile. Send messages using the same Messaging API as any other number type.
Sending messages from a short code
Once provisioned, send messages the same way as any other sender type:Short codes use ASCII 7-bit encoding by default (same character limits as GSM-7). See Message Encoding for details.
Automated responses
Short codes must handle standard keywords to pass carrier certification. Telnyx manages these automatically.Required keywords
Customizing responses
After carrier certification, you can customize the HELP and campaign keyword responses:Custom HELP response
Custom HELP response
Configure a custom help message that includes:
- Your business name
- What messages the user is subscribed to
- How to get support (phone number or email)
- How to opt out
Custom keyword response
Custom keyword response
When a user texts your campaign keyword (e.g., “JOIN”), they receive a confirmation message.Example:
Disabling automatic responses
Disabling automatic responses
After certification, you can disable automatic responses for HELP and campaign keywords to handle them yourself via webhook. Contact support@telnyx.com to request this change.
Use case examples
Two-factor authentication (2FA)
Two-factor authentication (2FA)
Keyword: N/A (API-triggered)
Flow: User initiates login → your app sends OTP via short code → user enters codeWhy short code: Highest deliverability, fastest delivery, trusted by carriers.
Marketing opt-in campaign
Marketing opt-in campaign
Keyword: JOIN
Flow: User texts JOIN to 12345 → receives welcome message → gets promotional messages
Emergency / mass notifications
Emergency / mass notifications
Keyword: ALERT
Flow: User opts in → receives critical alerts (weather, school closings, etc.)Why short code: Maximum throughput (1,000 MPS) for time-critical mass notifications.
Carrier certification requirements
Related resources
Choosing Your Sender Type
Compare short codes, toll-free, long codes, and alphanumeric sender IDs.
Rate Limiting
Short code throughput limits and queuing behavior.
Advanced Opt-In/Out
Customize opt-in and opt-out behavior.
Message Encoding
Understand ASCII 7-bit encoding used by short codes.