API Key

An API key is an authentication token used by an application to authenticate and authorize itself to invoke an API that is provided by an external service or resource. API keys can be very sensitive pieces of information, as they may allow an attacker to impersonate an authorized application or user, execute unauthorized transaction or, access confidential data. API keys should never be stored directly in code or in client-side applications, especially unencrypted, as this puts the keys at high risk of disclosure.