he four SMS sender types are short codes, long codes (US 10DLC), alphanumeric sender IDs, and toll-free numbers. The right one depends on whether you need two-way replies, how much throughput you send, and which countries you target: short codes and 10DLC handle US campaign traffic, alphanumeric IDs dominate one-way branded messaging across the GCC and Europe, and toll-free covers verified US and Canada two-way.
This is a decision guide for picking a sender. If you already know you need branded, regulator-approved IDs, skip to how sender ID registration works and the market-by-market worldwide registry map.
Short code: highest throughput, region-specific
A short code is a 5- or 6-digit number leased in one specific country and approved by its mobile operators and, in the US, the CTIA-administered short code registry. It is built for volume: short codes sustain the highest per-second throughput of any sender type, which is why they carry high-volume one-time-passcode and marketing programmes. They support two-way messaging and keyword opt-in/opt-out (JOIN, STOP). The trade-offs are cost and reach — a short code carries a recurring lease and a multi-week approval process, and it works only in the country it was provisioned for, so a global programme cannot standardise on a single code.
Long code and US 10DLC: standard two-way local numbers
A long code is an ordinary local phone number in the international E.164 format (see the ITU numbering plan). It supports natural two-way conversations from a number recipients recognise, which suits support, alerts, and appointment threads. In the United States, application-to-person traffic sent from a local number must run over the 10DLC (10-digit long code) framework: the brand and each campaign are registered with The Campaign Registry, and the throughput a number is allowed is tied to a trust score assigned during registration. Unregistered US long-code A2P traffic is heavily filtered, so registration is not optional there. See SMS API for how sender selection is set per message.
Alphanumeric sender ID: branded, one-way, the MENA and EU default
An alphanumeric sender ID replaces the number with up to 11 characters of brand text — the recipient sees your name, not a digit string. It is the most widely used sender type across the Gulf and much of Europe, where branded transactional messaging is expected. The defining limitation is that it is strictly one-way: because there is no number behind it, recipients cannot reply, so it cannot carry conversations or keyword STOP handling. In almost every market that uses it, the sender ID must be pre-registered with the regulator or operator and matched to your verified brand before it will deliver — TDRA in the UAE and the CST in Saudi Arabia run exactly this model. Alphanumeric IDs are not supported for domestic US traffic, so a US programme must fall back to a short code, 10DLC, or toll-free number.
In the GCC, alphanumeric sender IDs dominate and are mandatory to register: the UAE's TDRA and Saudi Arabia's CST both require every branded sender to be filed and tied to a trademarked entity before operators will deliver it, with unregistered IDs blocked at the network. Plan lead time into any launch — see the worldwide registry map.
Toll-free SMS: verified two-way for the US and Canada
A toll-free number (800, 888, 833, and similar prefixes) can be text-enabled to send and receive A2P SMS across the US and Canada. It supports two-way messaging and STOP-based opt-out at moderate throughput, and unlike 10DLC it does not require per-campaign registration — instead it goes through a one-time toll-free verification that reviews your brand, use case, and message samples. Verified toll-free is a common choice for North American two-way support and notifications that do not need a short code's peak volume.
The four sender types compared
| Sender type | Two-way? | Throughput | Typical use | Registration / availability |
|---|---|---|---|---|
| Short code | Yes | Highest | High-volume OTP and campaigns | Per-country lease + carrier approval; region-specific |
| Long code / 10DLC | Yes | Low–moderate (US: trust-score based) | Two-way support, alerts, conversations | US: brand + campaign registration (10DLC); a local number per market |
| Alphanumeric sender ID | No (one-way) | High | Branded OTP and notifications | Pre-registered with regulator/operator; common in GCC and EU; not US domestic |
| Toll-free | Yes | Moderate | US/CA two-way support and alerts | One-time toll-free verification; US and Canada only |
Two-way versus one-way, and opt-out handling
The two-way question usually decides the shortlist before cost does. Short codes, long codes, 10DLC, and toll-free all have a real number behind them, so recipients can reply and you can honour keyword opt-out (STOP, UNSUBSCRIBE) inside the same thread — which most consumer-protection rules require for marketing. An alphanumeric sender ID cannot receive anything, so opt-out has to be handled another way: an in-message instruction pointing to a link or a separate reply channel, and a suppression list you maintain yourself. If a use case genuinely needs conversation or in-channel STOP, alphanumeric is the wrong sender regardless of how good the branding looks.
How to choose
- Do recipients need to reply, or must opt-out happen in-channel? If yes, rule out alphanumeric and use a short code, long code/10DLC, or toll-free.
- Sending domestic US A2P? Choose a short code for peak-volume campaigns, 10DLC for standard two-way at lower volume, or verified toll-free for two-way support — alphanumeric is not available.
- Sending to the GCC, wider MENA, or Europe? A registered alphanumeric brand sender is the expected default for transactional and OTP traffic — file it with the regulator first.
- Need the highest sustained throughput or big OTP bursts in a single country? A short code is purpose-built for it, at the cost of a lease and approval.
- Running a global programme? Expect to mix sender types per market — alphanumeric where it is standard, 10DLC/toll-free/short code in North America — and orchestrate them behind one API rather than one universal sender.
BroadNet has run direct A2P routes since 2003 to 200+ countries through 1,000+ operator connections at a 99.99% platform SLA, sustaining up to 30,000 SMS/sec per node — and provisions and registers the right sender type per market, from GCC alphanumeric IDs to US 10DLC and toll-free. See A2P SMS to match senders to your destinations.
Frequently asked questions
What is the difference between a short code and a long code?
A short code is a 5- or 6-digit number leased in one country for high-throughput campaign and OTP traffic, requiring carrier approval and a recurring lease. A long code is a standard local phone number that supports natural two-way conversations at lower throughput and lower cost. In the US, A2P traffic on a long code must be registered under the 10DLC framework.
What is an alphanumeric sender ID?
An alphanumeric sender ID is a sender made of up to 11 characters of brand text — the recipient sees your name instead of a number. It is one-way, so recipients cannot reply, and it is the default for branded transactional and OTP messaging across the GCC and much of Europe. Most markets require it to be pre-registered with the regulator or operator, and it is not supported for domestic US traffic.
Which SMS sender type should I use?
Start from two-way and geography. If recipients must reply or opt out in-channel, use a short code, long code/10DLC, or toll-free. In the GCC and Europe, a registered alphanumeric brand sender is standard for one-way OTP and notifications. For domestic US traffic use a short code for volume, 10DLC for standard two-way, or verified toll-free. Global programmes mix senders per market behind one API.
References
- CTIA — Messaging Principles and Best Practices and US short code guidance: ctia.org
- ITU — E.164 international public telecommunication numbering plan: itu.int
- UAE TDRA and Saudi CST — national sender-ID registration requirements (see our summary): BroadNet worldwide registry map.
- BroadNet — sender ID registration and the SMS API for setting the sender per message.