---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/api/errors/16025#article
headline: "16025: Dial->Conference: Participant label is in use by another participant"
url: https://www.twilio.com/docs/api/errors/16025
inLanguage: en
dateModified: 2026-06-08T11:38:30.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 16025: Dial->Conference: Participant label is in use by another participant

Log Type: APPLICATION

Log Level: ERROR

## Description

This error occurs when `<Dial><Conference>` sets `participantLabel` to a value that is already used by another active participant in the same conference. `participantLabel` must be unique across all participants in a conference. If Twilio detects a duplicate label, Twilio does not add the call to the conference and continues to the next TwiML verb.

### Possible causes

* Your application assigned the same `participantLabel` to more than one inbound caller joining the same conference through `<Dial><Conference>`.
* Your application generated or reused a label that is already assigned to another active participant in that conference.
* The label is already in use by an active participant that was added to the conference through the Conference Participant API. `participantLabel` values must be unique across all participants in the conference, regardless of how each participant was added.

### Possible solutions

* Generate a `participantLabel` that uniquely identifies each participant in the conference.
* If you add participants through both `<Conference>` TwiML and the Conference Participant API, use one label naming strategy across both paths so the same value is not reused for another active participant.
* Review the active participants in the conference before you reuse a label. You can fetch, list, update, and delete active conference participants by label through the Participants subresource.
* Add fallback TwiML after `<Dial><Conference>` if you want the call to continue somewhere specific when Twilio rejects the duplicate label.

#### Additional resources

* [TwiML Voice: `<Conference>`](/docs/voice/twiml/conference)
* [Conference Participant API](/docs/voice/api/conference-participant-resource)
* [Debugging Your Twilio Application](/docs/usage/troubleshooting/debugging-your-application)