Save-Data

Save-Data

The Save-Data network client hint request header field is a boolean which indicates the client's preference for reduced data usage. This could be for reasons such as high transfer costs, slow connection speeds, etc.

A value of On indicates explicit user opt-in into a reduced data usage mode on the client, and when communicated to origins allows them to deliver alternative content to reduce the data downloaded such as smaller image and video resources, different markup and styling, disabled polling and automatic updates, and so on.

Syntax

Save-Data: <sd-token>

Directives

<sd-token>

A value indicating whether the client wants to opt in to reduced data usage mode. on indicates yes, while off (the default) indicates no.

Examples

The Vary header ensures that the content is cached properly (for instance ensuring that the user is not served a lower-quality image from the cache when Save-Data header is no longer present [e.g. after having switched from cellular to Wi-Fi]).

With Save-Data: on

Request:

GET /image.jpg HTTP/1.0
Host: example.com
Save-Data: on

Response:

HTTP/1.0 200 OK
Content-Length: 102832
Vary: Accept-Encoding, 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

Browser compatibility

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
Save-Data	49	≤79	?	?	35	No	49	49	?	35	No	5.0

See also

• Help Your Users `Save-Data` - CSS Tricks
• Delivering Fast and Light Applications with Save-Data - Google Developers
• Vary header which indicate that the content served varies by Save-Data (see HTTP Caching > Varying responses)
• CSS @media feature prefers-reduced-data
• Adapting to Users with Client Hints (developer.google.com)
• Network client hints
  • Downlink
  • RTT
  • ECT
• NetworkInformation.saveData