What is the role of an HTTP header?

The role of an HTTP header is to provide information about the data being sent between the client and server. HTTP headers convey essential details such as the type of content being transmitted (like HTML, JSON, or images), the length of the content, caching policies, and the type of browser making the request, among other things. This metadata helps both the client and the server understand how to process the data correctly, facilitating proper communication and resource handling during web interactions.

In this context, the other options don’t accurately reflect the primary function of HTTP headers. SEO optimization, data compression, and web page caching all play significant roles in web technology, but they are not directly tied to the main purpose of HTTP headers. Instead, they might involve different mechanisms, tools, or protocols that complement the overall web experience but do not define the fundamental role of HTTP headers.