In OAuth 2.0 RFC 6749, Authorization Request parameters are typically sent as URI query parameters via redirection in the user agent.
JWT-Secured Authorization Request (JAR) RFC 9101 provides solutions for the security challenges by allowing OAuth Clients to wrap Authorization Request parameters in a Request Object, which is a signed and optionally encrypted JSON Web Token (JWT) RFC 7519. In order to cope with the size restrictions, JAR introduces the request_uri parameter that allows OAuth Clients to send a reference to a Request Object instead of the Request Object itself.
Pushed Authorization Requests complements JAR by providing an interoperable way to push the payload of an Authorization Request directly to the Authorization Server in exchange for a Request_uri value usable at the Authorization Server in a subsequent Authorization Request.