They are called pseudo-headers. They are used to transfer the values of the traditional start line of requests and responses. As in HTTP/2 there is no such star

They are called pseudo-headers. They are used to transfer the values of the traditional start line of requests and responses. As in HTTP/2 there is no such start line they are encoded like other headers, but are using the colon in front of the key to denote them as pseudo-headers. Each request must contain all the required pseudo headers (:method, :path, :scheme) - same for the response. And no - this doesn't confuse a header parser since they are not parsed with an HTTP/1 header parser but with the HTTP/2 header tranmission mechanism (HPACK - as shown in the article). Before handing the request to your traditional web app the HTTP/2 server would remove those values from the set of received header fields and instead put them into the request struct.