Our complete API documentation is available here.
The current and latest version of the API is the Captain Data API v3.
This will show as https://api.captaindata.co/v3/
Make sure to always use the latest version of the API.
If you're having any trouble using this API, shoot us an email at support@captaindata.co.
If you're looking for the Documentation v2 (deprecated), check out https://docs.v2.captaindata.co