The Data Saver feature is described by Google as “a new system service that helps reduce cellular data use by apps, whether roaming, near the end of the billing cycle, or on a small prepaid data pack.” When enabled, “the system blocks background data usage and signals apps to use less data in the foreground wherever possible — such as by limiting bit rate for streaming, reducing image quality, deferring optimistic precaching, and so on.” It will be possible to whitelist apps to prevent them from being affected by the Data Saver mode.
The new system-level number blocking and call screening features make it much easier to block spammers, telemarketers, and other harassing callers in Android. Google says that any blocked numbers will be blocked from calling and sending text messages, and the list of blocked numbers can be accessed by multiple apps and is able to be backed up and restored when a device is reset. The new call screening feature goes one step further by preventing the call from ever making it to the call log or creating a notification.
Both Data Saver and number blocking have been in Google’s own apps, such as its dialer on Nexus devices and the Chrome browser, but this is the first time they’ve been made available on a system level, so all apps and device makers can take advantage of them. You can try the Android N preview now on most Nexus devices, while a full release is expected this fall.