The Handle server HTTP interface has in the past responded to requests in the native binary Handle protocol of RFC 3652. As of version 8 requests can also be made using a REST API, with requests and responses expressed via JSON encoding. This API may be useful for server administration or for developing applications using Handle, especially those not developed in Java and thus unable to use the Client SDK.

By default the Handle server HTTP interface will respond to requests using HTTP or HTTPS, on the same port. This is called "port unification" and was preferred in order to allow legacy servers to upgrade to v8 and receive the full benefits of the REST API without requiring a new port to be made available. Administrative operations using the REST API require the use of HTTPS.

Handle servers generally use self-signed certificates which can not be validated using the typical browser certificate validation. See "Authenticating the Server" in this chapter for one way to authenticate that the correct server has been reached.