The new Background Sync API improves reliability by allowing sites to schedule a sync the next time an Internet connection is available, even if the user is no longer on the page. Currently, if a user closes a tab before a task is finished, it would be lost. Sites often prevent this by showing a pop-up advising that closing the page would cancel whatever is happening. With the new API, the message would be sent regardless without the need of a warning.
Sites can send a lighter version of a webpage by checking if a user has a Save-Data header active. Additionally, users can also expect a smoother experience when scrolling with devices like a mouse wheel. All these features and more apply to the newest Chrome Beta on all platforms. Otherwise, they should be available in version 49 of Chrome in approximately six weeks.
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