Expose "Save-Data" client hint in navigator.connection about netinfo HOT 4 CLOSED

That's a good use case. My proposal would be to expose:

interface NetworkInformation : EventTarget {
    readonly attribute DOMString saveData;
};

The value would contain the token communicated in the Save-Data header. Today this would yield a single value of "on", but the IETF spec does allow us to define other token values and we should support that here as well.

/cc @marcoscaceres @jkarlin

from netinfo.

I wonder if one could just get the Save-Data client hint from the outgoing Request? That may allow modification of the Request's URL if need be upon the SW fetch event on a per Request basis without the need to expose this in the API.

The decision about what to store in the cache is generally made on "environmental conditions" and those are not enforceable with Save Data (unlike with something akin to Content Performance Policy).

The risk is that this signal is of limited value because it's not enforceable (similar to DNT) - which may end up confusing or frustrating user who set this, but then just get ignored by sites.

from netinfo.

Just to clarify something from @marcoscaceres's previous comment, this information would be most useful if it were available inside of a service worker's install handler, which is the event that's normally associated with precaching.

There's no Request exposed in the InstallEvent that's passed to the install handler.

from netinfo.

@igrigorik's proposed extension to NetworkInformation sounds great to me for the reason already mentioned by @jeffposnick (for SW decision making related to precaching). I can see it also being a good signal for adaptive video libraries to degrade quality somewhat to reduce network data use.

from netinfo.