| Name | Description | Type | Package | Framework |
| Extension | Interface for WebSocket Extensions. | Interface | org.eclipse.jetty.websocket.api.extensions | Jetty |
| ExtensionConfig | Represents an Extension Configuration, as seen during the connection Handshake process. | Class | org.eclipse.jetty.websocket.api.extensions | Jetty |
| ExtensionFactory | Class | org.eclipse.jetty.websocket.api.extensions | Jetty | |
| Frame | An immutable websocket frame. | Class | org.eclipse.jetty.websocket.api.extensions | Jetty |
| Frame .Type | Returns the enum constant of this type with the specified name | Class | org.eclipse.jetty.websocket.api.extensions.Frame | Jetty |
| IncomingFrames | Interface for dealing with Incoming Frames. | Interface | org.eclipse.jetty.websocket.api.extensions | Jetty |
| OutgoingFrames | Interface for dealing with frames outgoing to (eventually) the network layer. | Interface | org.eclipse.jetty.websocket.api.extensions | Jetty |