---
page_type: error
code: 21502
message: "21502: Invalid callback url"
level: ERROR
---

## Error - 21502

### Invalid callback url

The callback url provided is not a valid URL.

#### Possible Solutions

Make sure you submit a fully qualified URL including:

- protocol (http:// or https://)
- hostname
- file path
- properly url-encoded query parameters

Twilio must be able to reach this URL over the public Internet.