---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/api/errors/13233#article
headline: "13233: Dial->Conference: Invalid waitUrl"
url: https://www.twilio.com/docs/api/errors/13233
inLanguage: en
dateModified: 2026-06-08T11:38:30.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 13233: Dial->Conference: Invalid waitUrl

Log Level: WARNING

## Description

Set `waitUrl` on `<Conference>` to a well-formed relative or absolute URL, or set it to `''` if you do not want to play anything before the conference starts. The `waitUrl` endpoint can return an MP3 file, a WAV file, or a TwiML document.

### Possible causes

* You passed a `waitUrl` value that is not a well-formed URL.
* You provided a value that is neither a relative or absolute URL nor the empty string `''`.
* You intended to play hold audio or TwiML before the conference starts, but the `waitUrl` value does not point to a valid endpoint Twilio can request.
* You intended to disable waiting audio, but you used a placeholder or invalid value instead of the empty string `''`.

### Possible solutions

* Update `waitUrl` to a valid relative or absolute URL.
* If you do not want to play anything while callers wait for the conference to start, set `waitUrl` to `''`.
* Make sure the `waitUrl` endpoint returns supported content such as an MP3 file, a WAV file, or a TwiML document.
* If `waitUrl` returns TwiML, use only supported verbs such as `<Play>`, `<Say>`, `<Pause>`, and `<Redirect>`.
* If you need a simple hosted endpoint for valid TwiML, use a TwiML Bin and return properly formed TwiML from that URL.

#### Additional resources

* [TwiML `<Conference>`](/docs/voice/twiml/conference)
* [Voice Conference](/docs/voice/conference)
* [Get Started with TwiML Bins](/docs/serverless/twiml-bins/getting-started)