Delivering Fast and Light Applications with Save-Data
The Save-Data client hint request header available in Chrome, Opera, and Yandex browsers lets developers deliver lighter, faster applications to users who opt-in to data saving mode in their browser. Everyone agrees that faster and lighter web pages provide a more satisfying user experience, allow better content comprehension and retention, and deliver increased conversions and revenue.
https://developers.google.com/web/fundamentals/performance/optimizing-content-efficiency/save-data/#detecting_the_save-data_setting
