"invalid_grant" error when requesting an OAuth Token

Issue symptoms

When I attempt to obtain an access token, I receive the error:

{"error":"invalid_grant",
"error_description":"The provided access grant is invalid, 
expired, or revoked (e.g. invalid assertion, expired authorization 
token, bad end-user password credentials, or mismatching authorization 
code and redirection URI). 

Resolution steps

Check that the parameter used for the redirect URL is redirect_uri as shown below and replace the sections in italics with your data.

curl https://yoursubdomain.zendesk.com/oauth/tokens \
  -H "Content-Type: application/json" \
  -d '{"grant_type": "authorization_code", "code": "your_code",
    "client_id": "your_client_id", "client_secret": "your_client_secret", 
    "redirect_uri": "your_redirect_url", "scope": "read" }' \
  -X POST

Important: The parameter must be redirect_uri.

For more information, see the article: Using OAuth authentication with your application.