---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/api/errors/321403#article
headline: "321403: Invalid grant_type"
url: https://www.twilio.com/docs/api/errors/321403
inLanguage: en
dateModified: 2026-06-09T11:00:42.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 321403: Invalid grant\_type

Log Type: APPLICATION

Log Level: ERROR

## Description

Twilio could not process the token request because the `grant_type` parameter is missing or contains an unsupported value. For Client Credentials authentication, set `grant_type` to `client_credentials`.

### Possible causes

* The request does not include the `grant_type` parameter.
* The request includes a `grant_type` value other than `client_credentials`.
* The request body is malformed, so Twilio cannot read the `grant_type` parameter.
* The application is using a different OAuth flow than the endpoint supports.

### Possible solutions

* Include the `grant_type` parameter in the token request body.
* Set `grant_type` to `client_credentials`.
* Send the request using the expected content type and body format for the token endpoint.
* Review your IAM authentication flow and confirm that your application is using Client Credentials where required.

#### Additional resources

* [IAM documentation](/docs/iam)
* [Authenticate with Twilio APIs](/docs/iam/api)