> ## Documentation Index
> Fetch the complete documentation index at: https://developers.senderz.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Sender IDs overview

> Register and manage alphanumeric Sender IDs across global markets via API.

## What is a Sender ID?

A Sender ID (SID) is the alphanumeric name displayed as the sender when an SMS arrives on a recipient's handset. For example, `TrackFast` instead of a random phone number.

In markets with mandatory SID pre-registration (such as Australia under the ACMA SMS Sender ID Register), unregistered SIDs are replaced with `Unverified`. Registering your SIDs ensures your brand appears as intended.

## SID lifecycle

```
pending_review → pending_register → pending_brand_confirmation → registered
              └→ rejected                                      └→ suspended
                                                                └→ deregistered
```

| Status                       | Description                                                           |
| ---------------------------- | --------------------------------------------------------------------- |
| `pending_review`             | Submitted, awaiting Senderz validation                                |
| `pending_register`           | Validated, submitted to market register                               |
| `pending_brand_confirmation` | Awaiting brand owner confirmation (e.g. ACMA Assist/myID step for AU) |
| `registered`                 | Live on the register. Messages display the branded SID.               |
| `rejected`                   | Registration denied. See `rejection_reason`.                          |
| `suspended`                  | Temporarily suspended by register or Senderz.                         |
| `deregistered`               | Removed from register.                                                |

## SID rules

| Rule              | Value                                                                               |
| ----------------- | ----------------------------------------------------------------------------------- |
| Length            | 2-11 characters                                                                     |
| Characters        | Alphanumeric (A-Z, a-z, 0-9) and spaces                                             |
| Restriction       | Cannot be numbers only                                                              |
| Match requirement | Must match the brand's registered business name, company name, trademark, or domain |

## Market-specific validation

Validation rules are applied server-side based on the `market` field. For example, the AU market applies ACMA restricted-word checks and ABR cross-referencing. A `422` response with a market-specific error code is returned if rules are violated.

New markets are added by extending the market configuration. No API version change is required. Customers integrating against `/v1/` pick up new markets by passing the relevant country code.