# Caller ID Overview

Caller ID lets each party in a call see who is on the other end. This page explains the concept and describes the two kinds of caller ID that Cloud Voice works with, along with how the system decides which outbound caller ID to send.

## What caller ID is

Caller ID is a phone-service feature that passes a caller's number, and often their name, to the other party as the call connects, so the number and name appear on the receiving device.

:::note
A few terms are used throughout this page:

- **Trunk:** the connection between Cloud Voice and your phone carrier. Every call to or from the outside telephone network travels over a trunk.
- **Extension:** an internal user or device on the system, such as a desk phone, a softphone, or a Cloud Voice App account.
- **Outbound route:** the rule that decides which trunk an outgoing call uses (usually based on the number dialed).
:::

## Types of caller ID

Cloud Voice distinguishes between two directions of caller ID.

### Outbound caller ID

Outbound caller ID is the number shown to the person you are calling whenever an extension user places an external call. Every trunk carries a main number assigned by the carrier, and by default that is the number an external recipient sees.

If you want to present a different number, arrange the custom caller ID service with your trunk provider first, then configure the value in Cloud Voice. You can set outbound caller ID at several levels:

- Emergency Numbers
- Outbound Route
- Trunk
- Extension

:::caution
Customizing the outbound caller ID takes two steps, and both are required. You must purchase the custom caller ID service from your trunk provider **and** set the number in Cloud Voice. Entering a custom number in Cloud Voice on its own will not change what the recipient sees if the provider has not enabled the service on your trunk.
:::

For the full range of options and how to apply them, see [Customize Outbound Caller IDs for Outbound Calls](/pbx/administrator-guide/customize-outbound-caller-ids/).

### Inbound caller ID

Inbound caller ID is the external caller's number that appears on an extension user's phone when someone calls into Cloud Voice.

You can adjust how an incoming number is presented before it reaches the destination user. This is handled per trunk, so a reformatting rule applies to every call arriving on that trunk.

:::note
Reformatting is useful when a carrier delivers numbers in a format your users do not expect. Because the rule is tied to the trunk, you set it once and it affects all inbound calls on that trunk rather than a single extension.
:::

For details, see [Reformat Inbound Caller ID based on a Trunk](/pbx/administrator-guide/reformat-inbound-caller-id/).

## How Cloud Voice chooses the outbound caller ID

When an extension user dials out, the system first checks whether the call is an emergency call. It then selects the outbound caller ID to send using the order below, from highest priority to lowest. The first value that applies is the one presented to the recipient, so a higher entry always overrides a lower one.

1. Extension's emergency outbound caller ID
2. Trunk's emergency outbound caller ID
3. Outbound Route caller ID
4. Trunk's outbound caller IDs associated with the extension user
5. Trunk's general outbound caller ID
6. Trunk's default number supplied by the carrier
7. Extension's caller ID

:::danger
The two emergency caller ID entries sit at the top of this list, which means an emergency call uses them before anything else. The number sent on an emergency call is what the emergency operator (the Public Safety Answering Point, or PSAP) sees and uses to call the caller back. If it is blank or points to a number that cannot receive that callback, emergency response can be delayed. Verify the emergency outbound caller ID before you rely on it.
:::

:::note
If none of the higher entries are configured, the list falls through to the trunk's default number supplied by the carrier (item 6). That carrier number is the safety net that is always present, so a caller ID is sent even when nothing custom has been set.
:::

:::tip
To confirm which caller ID Cloud Voice will actually send, place a test call to a phone you control and check the number that appears. This is faster than tracing the priority list by hand and catches a misconfigured level before real callers see it.
:::