# Building connections
When connecting to an API, you must first authenticate your custom connector. To do this, you must "inform" the API that it can trust you and send potentially sensitive information to you.
Workato supports the following formalized forms of authentication. You can also add custom approaches to authenticate yourself. Read the documentation for the API to choose the form of authentication that is most suitable for the custom connector that you are building.
- Basic authentication
- API key Authentication
- Header Authentication
- JWT Authentication
- OAuth 2.0 Authentication (Auth code grant)
- OAuth 2.0 Authentication (Auth code grant with PKCE)
- OAuth 2.0 Authentication (Client Credentials)
- OAuth 2.0 Authentication (ROPC)
- AWS Authentication
- On-premise Authentication
- Custom Authentication
- Multiple Authentication formats in a single connector