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Playbook · 5 steps

A2P 10DLC(10DLC)

Also called: Ten-digit long code · 10DLC registration · US A2P 10DLC · Application-to-person 10-digit long code

5steps

Level
Practitioner
Reading time
About 6 min

Reviewed

Definition
The US scheme for business texting from ordinary 10-digit numbers, which requires brands and campaigns to register with carriers before sending.

01 · How it works, in 5 steps

How does A2P 10DLC work?

  1. 1

    Register the brand

    Submit the legal entity's details to The Campaign Registry through your SMS provider: exact legal name, tax or company registration number (non-US companies use their home-country number), address, website and vertical. A name that does not match official records is the commonest reason for failure.

  2. 2

    Get vetted if you need volume

    Basic registration puts the brand on the system. Additional vetting by a third party returns a score that carriers use to grant throughput; unvetted or low-scoring brands get the smallest allowances.

  3. 3

    Register each campaign

    Pick the use case that matches the traffic (2FA, account notifications, customer care, marketing or a mixed campaign) and supply sample messages, a description of the opt-in flow, and the opt-out and help replies. Carriers review it before it can carry traffic.

  4. 4

    Link numbers and send

    Assign your 10-digit numbers to the approved campaign. Messages now travel as registered traffic, and each carrier applies its own limit: a per-campaign messages-per-minute allowance at AT&T, a daily brand cap at T-Mobile.

  5. 5

    Pace sends and honour opt-outs

    Queue messages so bursts stay under the allowance, process STOP at once, answer HELP, and keep content inside the registered use case. Offers sent on a notifications campaign invite filtering.

02Try it

Hands-on: use the controls to work through it yourself.

Fire a sale-day burst at a campaign's carrier allowance

Refill +1.25 / s

0 / 75 tokens

Each dot = 2 tokens

Last burst · 200 texts

75 admitted — one token each. 125 rejected with HTTP 429 Too Many Requests: the bucket ran dry. Each chip ≈ 5 texts.

Tokens left
0
Admitted
75
Rejected (429)
125
Full again in
1 min
1.25 tokens / s

The bucket holds 75 tokens, so up to 75 texts can go out in one burst. After that, texts get through only as fast as tokens drip back in: 1.25 per second is the sustained limit. Watch the dots refill, then send another burst before it is full.

An illustrative campaign allowed 75 texts a minute, drawn as a bucket of 75 tokens refilling at 1.25 a second. Send a burst of 200 and see how many go at once and how many must wait or be refused.

A burst of 200 hit a full bucket of 75: 75 accepted, 125 rejected with 429.

03What is A2P 10DLC?

A2P 10DLC (application-to-person 10-digit long code) is the system US mobile carriers use for business text messaging sent from standard ten-digit phone numbers, the same kind of number a person has, rather than from a five- or six-digit short code or a toll-free number. Before a business can text US users from a 10DLC number, it registers itself as a brand and registers each kind of messaging it does as a campaign with The Campaign Registry (TCR), the industry hub the major US carriers rely on.

A brand record identifies the legal entity: exact legal name, tax or company registration number, address, website and industry, optionally put through additional vetting that returns a score. A campaign record describes one use case, such as two-factor authentication, account notifications, customer care or marketing, with sample messages, how subscribers opt in, and how STOP and HELP are handled. Carriers then use the use case and the vetting result to set throughput: AT&T gives each campaign a messages-per-minute allowance, and T-Mobile applies a daily message cap at brand level.

10DLC is the US counterpart to India's DLT Registration, but the two work differently. DLT registers the principal entity, its headers and the exact wording of every content template, and Indian operators match each SMS against that wording. 10DLC registers who is sending and what kind of messages they send, then relies on carrier filtering, opt-out rules and throughput caps. Since early 2025 US carriers block unregistered 10DLC traffic, so an Indian company texting US customers needs an approved campaign, a verified toll-free number or a short code before its first message.

Key takeaways

  • A2P 10DLC is the US system for business texts sent from ordinary 10-digit numbers, registered as a brand and a campaign before sending.
  • Brand registration identifies the company; campaign registration declares the use case, sample messages, opt-in method and STOP/HELP replies.
  • US carriers block unregistered 10DLC traffic and set each campaign's throughput from its use case and the brand's vetting result.
  • Unlike India's DLT, 10DLC does not register every message text: it registers who you are and what kind of messages you send.
  • Indian businesses need 10DLC, a toll-free number or a short code for US texts, because WhatsApp marketing templates are not delivered to US numbers.

04 · In code

A2P 10DLC in code

// Pace US texts under a campaign's carrier allowance and honour opt-outs at once.
// sendSms() stands for your SMS provider's client; numbers are E.164.
const PER_MINUTE = Number(process.env.CAMPAIGN_MSGS_PER_MIN ?? 75); // from your campaign's carrier details
const GAP_MS = 60_000 / PER_MINUTE;
const optedOut = new Set(); // load from your suppression list at start-up
 
export async function drain(queue) {
  for (const msg of queue) {
    if (optedOut.has(msg.to)) continue;               // never text an opted-out number
    await sendSms({ from: msg.from, to: msg.to, body: msg.body });
    await new Promise((resolve) => setTimeout(resolve, GAP_MS)); // stay under the allowance
  }
}
 
// Inbound-message webhook from your provider.
const STOP_WORDS = new Set(["STOP", "STOPALL", "UNSUBSCRIBE", "CANCEL", "END", "QUIT", "REVOKE", "OPTOUT"]);
 
export function onInbound({ from, body }) {
  const word = body.trim().toUpperCase();
  if (STOP_WORDS.has(word)) {
    optedOut.add(from); // persist it too: the opt-out covers every campaign
    return "You are unsubscribed and will receive no more messages.";
  }
  if (word === "HELP") {
    return "Clinic Billing alerts. Reply STOP to unsubscribe. Msg & data rates may apply.";
  }
}

Throughput is enforced by carriers, so pace in your own queue; opt-out keywords must stop all further texts immediately.

05 · Key facts

A2P 10DLC: key facts and limits

Full name
Application-to-person 10-digit long code
Registry
The Campaign Registry (TCR), via your SMS provider
What is registered
The brand (company) and each campaign (use case)
Throughput
AT&T: messages per minute per campaign; T-Mobile: daily brand cap
Unregistered traffic
Blocked by US carriers since early 2025
Required replies
STOP (opt-out) and HELP
Alternatives
Verified toll-free numbers, short codes

06 · Mistakes to avoid

Common mistakes with A2P 10DLC

  • Registering a name that does not match official records

    Vetting checks the legal name and tax or company number against official sources. Use the registered legal name, not the trading name, or the brand fails or scores low.

  • One mixed campaign for everything

    Mixed and low-volume campaigns get lower allowances and closer scrutiny. Separate login codes, notifications and marketing into their own campaigns so a filtered promotion cannot slow your login codes.

  • Sending content outside the registered use case

    A notifications campaign that starts carrying offers looks like spam to carrier filters. Register a marketing campaign for promotional texts and keep it separate.

  • Bursting past the allowance

    A sale announcement fired at full speed exceeds the per-minute allowance, and messages are delayed, queued or rejected. Pace the send in your own queue, as the scene shows.

  • Treating 10DLC like India's DLT

    There are no per-message template IDs to pass. Carriers judge sample messages, opt-in evidence and live traffic instead, so keep a consent record for every US recipient.

07Example: A Pune SaaS company texts its US customers

A Pune billing-software company sells to dental clinics in Texas and needs to text clinic owners login codes, payment-failure alerts and an occasional upgrade offer. Login codes go by WhatsApp authentication templates to owners who use WhatsApp, but the offer cannot: WhatsApp marketing templates are not delivered to US numbers. The team registers the company as a brand with its Indian company registration details, completes vetting, and registers three campaigns (two-factor authentication, account notifications and marketing) instead of one mixed campaign. Its queue paces alerts under the AT&T per-minute allowance, and STOP replies write straight to a suppression list that every campaign checks before sending.

08 · Why it matters

Why does A2P 10DLC matter?

For a business with US customers, such as an Indian SaaS company, an ed-tech platform with American learners or an exporter's after-sales desk, SMS is often the only text channel for some messages: WhatsApp marketing templates are not delivered to US numbers at all. 10DLC registration decides whether those texts arrive, how fast they can go out and how much carrier filtering they face. A weak or mismatched campaign means throttling and filtered messages; no campaign means nothing arrives.

09 · Pro tips

Best practices for A2P 10DLC

  • Write sample messages that look exactly like live traffic, including the brand name and the opt-out line.
  • Describe the opt-in wording and where the sign-up form lives in the campaign description.
  • Start every text with the brand name so recipients and filters recognise the sender.
  • Watch delivery reports per carrier: a drop at one carrier usually points to filtering, not a network fault.

1010DLC FAQs

Do Indian companies need 10DLC registration to text US numbers?+
Yes, if they send from ordinary US 10-digit numbers. Non-US companies register as brands with their home-country company details through their SMS provider; the alternatives are verified toll-free numbers and short codes.
What happens to unregistered 10DLC messages?+
US carriers block them. Since early 2025 unregistered application-to-person traffic on 10-digit numbers is not delivered, so register the brand and an approved campaign before the first send.
How is 10DLC different from India's DLT registration?+
10DLC registers the sender and the type of messaging; DLT registers the sender, its headers and the exact wording of every template. Indian operators match each SMS against a registered template ID, while US carriers judge campaigns, consent and traffic patterns.
Why is my 10DLC throughput so low?+
Throughput follows the campaign's use case and the brand's vetting result. Unvetted brands and mixed or low-volume campaigns get the smallest allowances; additional vetting and dedicated campaigns raise them.
Can I use WhatsApp instead of SMS for US customers?+
Partly. WhatsApp marketing templates are not delivered to US numbers, so promotions need SMS or another channel, while utility and authentication templates and replies inside the customer service window still go by WhatsApp.

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