Why were server-sent events introduced in HTML5?

Server-Sent Events (SSE) were introduced in HTML5 to provide a one-way communication channel from the server to the client. They allow the server to send data updates to the client over a long period without the client needing to constantly request new data (polling).

Main advantages of SSE:

• Efficiency: Less overhead compared to constantly recreating HTTP requests during polling.
• Simplicity: Easier to implement on the client and server side compared to WebSockets for one-way communication.
• Automatic Reconnection: The browser automatically attempts to restore the connection if it is lost.
• HTTP Support: Works over standard HTTP, simplifying the use of proxies and firewalls.

They are used for real-time updates that do not require two-way communication, such as:

• News feeds
• Stock quotes
• Notifications
• Server logs

Unlike WebSockets, SSE does not support sending data from the client to the server directly over the same connection. For two-way communication, WebSockets are preferred.