Get application id from user access token (or verify the source application for a token)

Solution 1:

https://graph.facebook.com/app/?access_token=[user_access_token]

This will return the app this token was generated for, you can compare that against your app's id.

Solution 2:

The official graph endpoint for inspecting access tokens is:

GET graph.facebook.com/debug_token?
      input_token=[user_access_token]&
      access_token=[app_token_or_admin_token]

Example response:

{
    "data": {
        "app_id": 138483919580948, 
        "application": "Social Cafe", 
        "expires_at": 1352419328, 
        "is_valid": true, 
        "issued_at": 1347235328, 
        "metadata": {
            "sso": "iphone-safari"
        }, 
        "scopes": [
            "email", 
            "publish_actions"
        ], 
        "user_id": 1207059
    }
}

app_token_or_admin_token can be obtained using the Graph API call:

GET graph.facebook.com/oauth/access_token?
     client_id={app-id}
    &client_secret={app-secret}
    &grant_type=client_credentials

The debug_token endpoint will fail if that user_access_token doesn't belong to the app that generated the app_token_or_admin_token.

Relevant facebook documentation:

• Inspecting access tokens: https://developers.facebook.com/docs/facebook-login/login-flow-for-web-no-jssdk/#checktoken

• App Tokens: https://developers.facebook.com/docs/facebook-login/access-tokens/#apptokens