[lloeki]

I suppose even fewer people have heard that Transfer-Encoding: chunked supports chunk extensions, which allows one to supply arbitrary metadata without trailers.

https://datatracker.ietf.org/doc/html/rfc2616#section-3.6.1

Ever went to some site that generates compressed downloads or database exports on the fly, got no progress bar as a result, and were severely annoyed by that lack of feedback? I was, so I used chunk extensions to submit a draft to emit progress information dynamically:

https://datatracker.ietf.org/doc/html/draft-lnageleisen-http...

As noted at the end of the draft, this could be generalized and extended to have additional capabilities such as in flight integrity checks, or whatever you can think of.