The HTTP Save-Data request header is a client hint that is sent to convey a preference for reduced data transmission.
The HTTP Save-Data request header is sent by a client to indicate that it wants to keep data transfer to a minimum. This may be the result of slow transfer speeds, where the client wants to have the best possible throughput for relevant data.
This is considered to be a low-entropy client hint, and therefore can be sent by the client even in cases where the server does not specifically request it using an HTTP Accept-CH response header.
The only directives are
off being the default value. An example of saving data is sending an image with a lower resolution. It may not be ideal for all purposes but it is sufficient for the client’s immediate needs.
The HTTP Save-Data header is a client hint that can be used to ask the server to reduce used to inform the client