HTTP headers are data exchanged between browsers and servers during communication via the Internet Protocol. Request headers are sent from the browser to the server, while response headers are sent from the web server to the requesting browser. Some request headers allow the browser to communicate information such as the preferred language, accepted content formats, and supported fonts. For example, the Content Acceptance header is a specific type of HTTP request header.

HTTP response headers are generated by the server and precede the HTML content. They contain details about the transmitted content, cookie management, any redirects, and cache information.