# 30123: Callback URL is missing

Log Type: APPLICATION

Log Level: ERROR

## Description

This error occurs when a Messaging configuration or request does not include the required `callbackUrl` value. In Messaging Link Shortening, the `Callback URL` is the URL Twilio uses to send click event data after a recipient clicks a shortened link.

### Possible causes

* You did not include the `callbackUrl` field in the request.
* You left the `CallbackUrl` value out of the Link Shortening domain configuration that Twilio uses for Messaging.

### Possible solutions

* Add a `CallbackUrl` value when you create or update the Link Shortening domain configuration. Twilio accepts `CallbackUrl` in the domain Config subresource.
* In the Console, open the domain configuration and fill in the Click tracking callback URL field, then save your changes.
* If you are using the REST API, include `CallbackUrl` in the request payload instead of leaving it blank.

#### Additional resources

* [Link Shortening Onboarding Guide](/docs/messaging/features/link-shortening/onboarding-guide)
* [Services resource](/docs/messaging/api/service-resource)