In RFC 7230, there's chapter 4.4:
When a message includes a message body encoded with the chunked transfer coding and the sender desires to send metadata in the form of trailer fields at the end of the message, the sender SHOULD generate a Trailer header field before the message body to indicate which fields will be present in the trailers. This allows the recipient to prepare for receipt of that metadata before it starts processing the body, which is useful if the message is being streamed and the recipient wishes to confirm an integrity check on the fly.
Trailer = 1#field-name
This reads to me like the Trailer header could be generated by a server as well as by a client.
If I were implementing HTTP in a server that gets accessed by regular clients (i.e. browsers): is there a real need to be prepared to receive trailing headers? Are there any browsers that are really using this? Or is this something I could implement with a custom client but is not used by regular clients in the real world?
