---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/api/errors/80405#article
headline: "80405: Participant Sid Invalid"
url: https://www.twilio.com/docs/api/errors/80405
inLanguage: en
dateModified: 2026-06-08T12:04:59.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 80405: Participant Sid Invalid

Log Level: WARNING

## Description

This warning appears when you pass an invalid Participant SID to a Proxy request. Proxy Participant resources use SIDs with the `KP` prefix, and Twilio SIDs are 34-character identifiers made up of a two-letter prefix followed by 32 hexadecimal characters.

### Possible causes

* The `Sid` or `ParticipantSid` value does not use the required `KP` prefix.
* The Participant SID is not 34 characters long.
* The value contains invalid characters, such as non-hexadecimal characters or extra whitespace.
* You passed a different resource SID, such as a `KS` Service SID, `KC` Session SID, or `KI` Interaction SID, where a Participant SID is required.
* You are not using the Participant SID returned when you created or fetched the Proxy Participant resource.

### Possible solutions

* Use the Participant SID returned by the Proxy Participant resource before making follow-up requests.
* Validate the Participant SID format before sending the request. Use the pattern `^KP[0-9a-fA-F]{32}$`.
* Confirm that you pass the Participant SID only in endpoints that require a participant resource, such as `/Participants/{Sid}` or `/Participants/{ParticipantSid}/MessageInteractions`.
* Keep `ServiceSid`, `SessionSid`, and `ParticipantSid` in separate parameters and do not substitute one resource SID for another.
* If you are sending a message through Proxy, create or list the session participants first, then use the correct `ParticipantSid` for the target participant.

#### Additional resources

* [Proxy Participant API reference](/docs/proxy/api/participant)
* [Sending Messages with Proxy](/docs/proxy/api/sending-messages)
* [What is a String Identifier (SID)?](/docs/glossary/what-is-a-sid)