How do I solve an API Gateway REST API endpoint “Missing Authentication Token” error?

problem

When I try to use an Amazon API Gateway REST API, I receive a 403 "Missing Authentication Token" error message. How can I resolve these issues?

how do I check the API Gateway response when a request is been made to a method after returning a Missing Authentication Token error?

what could be the cause?

API Gateway REST API endpoints return a Missing Authentication Token error for the following reasons:

• An API request was made to a method or resource that does not exist.
• The API is either set up with a changed Gateway response or the response comes from a backend integration.
• API requests are not signed when AWS Identity and Access Management (IAM) authentication is turned on for API methods.

How do I resolve it

Check that you are delivering the proper HTTP method request to your REST API endpoint.

A GET HTTP method request is automatically sent when testing a REST API endpoint from a web browser.

To test the POST HTTP method request, use another HTTP client. For instance, postman or curl.

POST HTTP method request example curl command

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

Example of using Postman POST HTTP method request