Evolution of HTTP - HTTP
the introduction of client-hints allows the browser, or client, to proactively communicate information about its requirements, or hardware constraints, to the server.

Save-Data - HTTP
ncoding, save-data cache-control: public, max-age=31536000 content-type: image/jpeg [...] without save-data request: get /image.jpg http/1.0 host: example.com response: http/1.0 200 ok content-length: 481770 vary: accept-encoding, save-data cache-control: public, max-age=31536000 content-type: image/jpeg [...] specifications specification title draft-grigorik-http-client-hints-03, section 7: save-data http client hints ...