About Wi-Fi Assist in iOS 9
In iOS 9, Apple introduced a new feature called Wi-Fi Assist, which is available on any cellular-capable device and is enabled by default. The idea behind it is that if the device’s Wi-Fi signal is unreliable, then it automatically switches to a cellular data connection, instead of trying to work with the wonky Wi-Fi connection. There are some limits on Wi-Fi Assist in order to prevent it from using too much data: audio and video won’t stream, background downloads are paused, and email attachments will not download.
Despite those limits, many users have experienced high cellular data usage with Wi-Fi Assist enabled. If you have a problem with chewing through too much cellular data—or worry that you might—unless you have a specific need for Wi-Fi Assist, I highly recommend disabling it in Settings > Cellular. You’ll find the Wi-Fi Assist switch way at the bottom of the Cellular screen.
Posted by Josh Centers (Permalink)