SSE are uncomplicated and specific. They are to be used when the majority of data transfer proceeds unidirectionally from a server to clients. A traditional and similar concept is the push technology. SSE pass text messages with simple formatting. Many types of applications passively receive brief status updates or data state changes. SSE are an excellent fit for these types of applications.
Like WebSocket, SSE also eliminate the redundant chatter of AJAX. Unlike WebSocket, an SSE connection is only concerned with broadcasting data from servers to connected clients:
A client connects to a server supporting SSE by passing the EventSource constructor a path:
let eventSource = new EventSource('/login');
This instance of EventSource will now emit subscribable data events whenever new data is received from the server.