Why most API paginations do not rely on HTTP Range header?

Question

I\'ve searched a lot but I can\'t find a good answer to this question. Being a HATEOAS aficionado, I would think that this header fit perfectly:

    Range: item=         


        

Answer 1

Here the answers that I gently borrowed from this question thanks to @ptidel: Content-Range header - allowed units?.

First, custom units are proposed in this draft HTTP/1.1, part 5: Range Requests and Partial Responses

Second, there is a subtle difference, the first statement has been made for parsing purpose

    range-unit       = bytes-unit | other-range-unit
    bytes-unit       = "bytes"
    other-range-unit = token

While the second statement has been made for producing HTTP request.

Finally, the whole comment from Ferenc Mihaly summarizes perfectly the situation:

I conform to the HTTP spec when I'm sending [a custom range unit] and they conform to HTTP when they ignore it

WebDAV uses HTTP extensions correctly, IMO, but rarely works over the Internet for exactly this reason