Why are headers needed? It seems that this information can be transmitted in the body.

Headers in HTTP are used to transmit meta-information about the request or response, which is not directly related to the content (body). They are needed for:

• Defining the type and format of data (e.g., Content-Type: application/json).
• Managing caching, authentication, sessions (e.g., Authorization, Cookie).
• Transmitting information about the client and server (User-Agent, Server).
• Managing connection behavior (e.g., Keep-Alive).

It is not practical to transmit such information in the body, as the body is intended for the main content, and headers allow servers and clients to quickly and standardizedly process requests and responses without the need to parse the body.