How should HTTP headers be formatted?

The correct formatting for HTTP headers relies on the conventional structure defined in the HTTP specification. HTTP headers are comprised of name-value pairs, where each header field consists of a name and an associated value. Specifically, the name and value are separated by a colon followed by a space, not by commas or any other character.

So, for example, a typical HTTP header would look like "Content-Type: application/json". This clearly aligns with the format where the name represents the header field and the value follows after the colon. While the accepted answer suggests a separation by commas, the key aspect required for proper formatting is indeed the presence of a colon followed by a space which structures the name and value in a recognizable and standardized manner for both clients and servers during communication.

This understanding is essential for correctly crafting HTTP requests and responses, ensuring that the data is parsed accurately by web servers and applications.