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Glossary · Compliance

What is A2P 10DLC?

  • Also called: 10dlc, a2p calling, what is a2p calling

Reviewed by Sujan ThapaliyaLast updated

Definition

A2P 10DLC is the US framework for sending application-to-person messages over ordinary 10-digit long codes. Businesses register a brand and each messaging campaign with the carriers, which sets throughput limits and determines whether messages are delivered or filtered.
The three STIR/SHAKEN attestation levels, which underpin how a2p 10dlc behaves in practice: A asserts both that the carrier knows the customer and that the customer may use the calling number, B asserts the customer only, and C asserts neither. A shared number pool can reach B at best, which is why number ownership keeps recurring in these definitions.
Attestation is the backdrop to most caller-ID and deliverability terms, a2p 10dlc included.

In practice

How a2p 10dlc actually works

Unregistered A2P traffic is filtered heavily and often silently; messages report as sent and never arrive.

Registration assigns a trust score that governs message throughput per second and daily volume. Score improves with verified business details and clean opt-in practice.

'A2P calling' as a search term usually means the voice analogue: automated calls originated by software rather than dialled by a person, which carriers treat with the same scrutiny.

Registration is also use-case-bound rather than a one-off. Traffic that drifts away from the registered campaign — a support line that starts sending promotions — degrades over weeks as carriers reclassify it. Re-registering the campaign you are actually running is the fix, not increasing send volume to compensate.

Worked example

An unregistered campaign typically shows healthy delivery receipts and near-zero engagement — because the messages were filtered after the receipt. That gap between receipts and replies is the tell.

A2P 10DLC: common questions

What is 10DLC registration?
Registering your brand and each messaging campaign with the carriers so that application-to-person traffic sent from ordinary ten-digit numbers is recognised as legitimate. Unregistered A2P traffic is filtered aggressively, which looks like messages simply vanishing.
How long does 10DLC registration take?
Brand registration is usually quick; campaign vetting takes longer and varies by use case, with higher-scrutiny categories taking the longest. Start it before you advertise the number rather than after messages stop arriving.
What happens if I skip registration?
Throughput is throttled and messages are filtered, often silently. You will see delivery receipts that look acceptable while recipients receive nothing, which is the worst possible failure mode because it hides itself.

Sources

  1. Combating Spoofed Robocalls with Caller ID Authentication — Federal Communications CommissionThe STIR/SHAKEN framework, the attestation levels carriers sign calls with, and the mandate requiring providers to authenticate caller ID.
  2. 47 U.S.C. § 227 — Restrictions on the use of telephone equipment — Cornell Legal Information InstituteThe Telephone Consumer Protection Act itself — the consent requirements, calling-hours limits, and private right of action.
  3. ITU-T Recommendation E.164 — The international public telecommunication numbering plan — International Telecommunication UnionThe international number format, the 15-digit maximum, and how country codes and national numbers compose.

See a2p 10dlc in the product

Business SMS lets your team send and receive texts from the same numbers you call from, in one shared inbox. In the US, application-to-person texting requires 10DLC brand and campaign registration. Without it, carriers filter your messages before anyone sees them.

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