The Numeral API uses API keys to authenticate requests. The API key must be passed in the X-API-Key HTTP header of your API calls. Do not share your API key in publicly accessible areas, such as GitHub, client-side code, and so forth.

All API requests must be made over HTTPS. API requests made over plain HTTP will fail. API requests without authentication will also fail.

In addition to API keys and HTTPS, the Numeral API supports mutual TLS.