---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/api/errors/21456#article
headline: "21456: Invalid CallbackUrl"
url: https://www.twilio.com/docs/api/errors/21456
inLanguage: en
dateModified: 2026-03-11T20:01:16.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 21456: Invalid CallbackUrl

Log Level: ERROR

## Description

The callback URL given to callback after validation isn't a valid URL.

### Possible causes