One of iOS 9's many new features is designed to make the universally bad experience of using a poor Wi-Fi connection more bearable. It could also cause a major headache (and serious cash) for iPhone owners without an unlimited data plan.
The feature is called Wi-Fi Assist, and it's enabled by default when you upgrade to iOS 9 on any iPhone or cellular-equipped iPad. When a Wi-Fi connection becomes poor or its signal gets weak, Wi-Fi Assist will automatically switch to a cellular connection for all internet usage.
That can be great for maintaining a solid internet connection, but it could also spell trouble for those trying to conserve their cellular data.
People have been tweeting about a sudden spike in data usage once they upgraded to iOS 9, with WiFi Assist seeming to be the culprit.
—Jim Ray (@jimray) September 24, 2015
—Alex Heath (@alexeheath) September 28, 2015
If you're concerned about your data usage increasing, you can check usage for your billing period under the "Cellular" section of the Settings app. You'll also see an option there to turn off Wi-Fi assist.
Apple could help alleviate the issue by disabling Wi-Fi Assist by default and positioning the feature more prominently in Settings (it's currently buried under the entire list of apps that use data in the Cellular section). Until then, it's helpful to exercise caution and know how your iPhone is handling your data usage.
