All API requests must be authenticated using API keys. You can authenticate your requests by adding an Authorization header with a Bearer token type as shown below, replacing the random string with your sandbox or live API key. 
Authorization: Bearer sk_site_e66e03bf9a807c88dd3dfa0f893de60b

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Example Request

Here’s an example of how to make an authenticated request to the Billingrails API: 
curl -X GET 'https://sandbox-api.billingrails.com/v1/accounts' \
  -H 'Authorization: Bearer YOUR_API_KEY'