How do I troubleshoot 403 "Missing Authentication Token" errors from an API Gateway REST API endpoint?

Last updated: 2021-03-24

API Gateway REST API endpoints return Missing Authentication Token errors for two reasons:

• The API request is made to a method or resource that doesn't exist.
• The API request isn't signed when the API method has AWS Identity and Access Management (IAM) authentication turned on.

To troubleshoot the error, do the following:

Confirm that there's a method and resource configured in the API Gateway resource path

For more information, see Set up a method using the API Gateway console.

Note: You must deploy the API for the changes to take effect.

(For APIs with a proxy resource integration) Confirm that there's a method configured under the root resource if the method request is sent to the root resource

For more information, see Set up API resources.

Confirm that the API request is signed if the API method has IAM authentication turned on

For more information, see Signing requests.

Confirm that you're sending the correct HTTP method request to the REST API endpoint

Testing a REST API endpoint directly from a web browser automatically sends a GET HTTP method request. Use a different HTTP client to test a POST HTTP method. For example, Postman or cURL.

The following is an example cURL command that uses the POST HTTP method request:

$  curl -X POST  <API URL> -d <request body>