Card91 has two environments
Sandbox API Host: https://api-sandbox.card91.io
Sandbox is used in development. No financial transactions happen on Sandbox, and we provide API's / UI to do dummy transactions to test your API integrations.
Live API Host: https://api.card91.io
This is the LIVE environment on which real financial transactions happen. Calls on this environment may incur a charge, so please do not use this in development.