Add Save-Data

Author: Elchi3

features/draft/spec/savedata.yml

@@ -0,0 +1,6 @@
+name: Save-Data
+description: When a client enables a data-saving mode, the browser sends a `Save-Data` request header which should be used as a signal to reduce data sent to the client. If enabled, websites are encouraged to deliver alternative content, such as smaller image and video resources, different markup and styling, or disabled polling.
+spec: https://wicg.github.io/savedata/
+compat_features:
+  - api.NetworkInformation.saveData
+  - http.headers.Save-Data