Sender ID explained
A sender ID is the 'from' identity a recipient sees on an A2P SMS: an alphanumeric string of up to 11 GSM-7 characters (typically a brand name), a numeric long code, or a short code. Most countries require alphanumeric sender IDs to be pre-registered with the regulator or operator before traffic will deliver.
Summarised from What is a sender ID?
How it works
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Pick the sender type
Alphanumeric IDs are one-way and suit OTPs and notifications; long codes are two-way and support replies; short codes offer the highest throughput for large campaigns. Some markets, notably the United States, do not allow alphanumeric IDs at all.
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Choose a compliant ID
Keep it to 11 GSM-7 characters, with no spaces in most markets, and match your brand name — generic strings like INFO, ALERT or OTP are commonly rejected. Decide up front whether it is transactional or promotional.
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Register it in each market
Submit your brand identity, the exact sender ID, the use case and sample content (plus proof of opt-in for marketing) through your aggregator. The regulator and/or operators approve, ask for clarification or reject; requirements and lead times differ by country.
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Send consistently
Operator firewalls drop unregistered sender IDs, and content that contradicts the registered classification can get an ID suspended, often within hours. Aggregator-side whitelisting stops anyone else sending under your name.
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Key terms
Each term has its own answer page with the full explanation.
- What is a sender ID?A sender ID is the 'from' identity a recipient sees on an A2P SMS.
- How do I register an alphanumeric sender ID?Most regulators require alphanumeric sender IDs to be pre-registered before any A2P SMS is accepted, so registration is a prerequisite, not an option.
- What are SMS sender ID best practices?Register alphanumeric sender IDs in every market that requires it, keep the ID to a recognizable brand name (up to 11 GSM-7 characters), classify traffic correctly as transactional or promotional, use it consistently…
- What is sender ID spoofing?Sender ID spoofing is sending an SMS with a falsified originator — appearing as `BANK-OF-X`, `DHL`, `MyBrand` when the sender has no authorisation to use that string.
- Short code vs long code — when to use eachA short code is a 3-6 digit number leased from a country regulator/operator for high-volume A2P SMS (typically marketing campaigns, voting, donations).
- What is a verified sender?A verified sender is a business messaging identity that a channel has authenticated and bound to a real brand — an RCS/RBM verified agent with logo and checkmark, a verified WhatsApp Business, or a registered SMS…
- What is A2P 10DLC?A2P 10DLC (10-digit long code) is the US carrier framework that lets businesses send application-to-person SMS from standard 10-digit local numbers, provided the brand and each campaign are registered with The…
- Sender ID registration in the UAE — the TDRA processEvery alphanumeric sender ID used to send A2P SMS to UAE mobile numbers must be pre-registered with the TDRA (Telecommunications and Digital Government Regulatory Authority).
- Sender ID registration in Saudi Arabia — the CST processAll A2P SMS to KSA mobile numbers must use a CST-registered alphanumeric sender ID.
- Sender ID registration in Egypt — the NTRA processEgypt's NTRA (National Telecommunications Regulatory Authority) requires all A2P SMS sender IDs to be pre-approved and all A2P traffic to terminate through NTRA-licensed local aggregators.
- Sender ID registration in Jordan — the TRC processJordan's TRC (Telecommunications Regulatory Commission) requires sender-ID pre-registration for all A2P SMS to Jordanian mobile numbers.
Regulations by country
Country rules that apply to this topic, from our regulations library.
Guides and further reading
- ArticleSender ID registration in the GCC — a market-by-market guide
- ArticleSender ID registries worldwide — 2026 compliance map
- ArticleUAE TDRA sender-ID registration in 2026: a practical compliance guide
- ArticleSaudi Arabia sender-ID rules — what the CST (formerly CITC) requires in 2026
- ArticleShort code vs long code vs alphanumeric sender ID vs toll-free: choosing an SMS sender type
- ReferenceVerified and branded sender messaging
- ToolSender ID Validator
Frequently asked questions
How do I register an alphanumeric sender ID?
Most regulators require alphanumeric sender IDs to be pre-registered before any A2P SMS is accepted, so registration is a prerequisite, not an option. The general path is: choose a compliant sender ID (up to 11 GSM-7 characters), submit your brand, use case, and sample content, then wait for regulator/operator review. Requirements and lead times differ by country — see the country guides for the exact process in each market.
Read the full answerWhat are SMS sender ID best practices?
Register alphanumeric sender IDs in every market that requires it, keep the ID to a recognizable brand name (up to 11 GSM-7 characters), classify traffic correctly as transactional or promotional, use it consistently so customers learn to trust it, and never send content that contradicts the registered use case. A well-managed sender ID lifts trust and delivery; a mismatched one gets suspended by the operator firewall.
Read the full answerWhat is sender ID spoofing?
Sender ID spoofing is sending an SMS with a falsified originator — appearing as `BANK-OF-X`, `DHL`, `MyBrand` when the sender has no authorisation to use that string. It is the SMS equivalent of email phishing, and it is the dominant vector for smishing attacks globally. The protocol weakness: GSM SMS has no end-to-end sender authentication, so the SMSC accepts whatever sender ID the originating ESME submits.
Read the full answerWhat is a verified sender?
A verified sender is a business messaging identity that a channel has authenticated and bound to a real brand — an RCS/RBM verified agent with logo and checkmark, a verified WhatsApp Business, or a registered SMS sender ID. Verification proves the message genuinely comes from the brand, closing the sender-ID spoofing gap that makes unauthenticated SMS a smishing vector. It is central to both trust and A2P monetization.
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