The Cal.com API uses API keys to authenticate requests. You can view and manage your API keys in your settings page under the security tab in Cal.com. API Keys are under Settings > Security Test mode secret keys have the prefix cal_ and live mode secret keys have the prefix cal_live_. Your API keys carry many privileges, so be sure to keep them secure! Do not share your secret API keys in publicly accessible areas such as GitHub, client-side code, and so forth. Authentication to the API is performed via URL Query Params. Provide your API key as a query param like: https://api.cal.com/v1/?apiKey=cal_live_xxxxxx All API requests must be made over HTTPS. Calls made over plain HTTP will fail. API requests without authentication will also fail.