When the Save-Data HTTP header is present, disable high quality (2x pixel density) thumbnails. This is normally set when "Data Saver mode" is enabled on Android, or "Lite mode" is enabled in Chrome. This setting can also be set using the `save_data` URL param or HTTP cookie. This is mainly for testing. The <body> tag has a `current-user-save-data` data attribute that indicates whether save data mode is on. https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Save-Data https://developers.google.com/web/fundamentals/performance/optimizing-content-efficiency/save-data/#the_save-data_request_header https://source.android.com/devices/tech/connect/data-saver
Components
Components are used to encapsulate common UI widgets used throughout the site. This includes things like comments, tag lists, post thumbnails, paginators, and other things used repeatedly throughout the site. Components encapsulate a widget's HTML, CSS, and Javascript together so that all the code for a component is in a single place.
This uses the ViewComponent library.
Components are similar in concept to React components.