Q: You recently wrote that iPhone users can control whether an app uses a Wi-Fi network or the cellular network (see tinyurl.com/kfwpjsk). How can I do that, and what are the benefits?
Chris Shea, Jacksonville, Fla.
A: The biggest reason to use a Wi-Fi network rather than a cellular connection is to save money.
Cellular downloads use up your phone plan's monthly allotment of wireless data. If you go over your data limit, you pay a penalty.
Wi-Fi has no monthly data limits, and is essentially a free service. If you use Wi-Fi at home, it's included in the monthly cost of your wired internet connection. If you use Wi-Fi in a public place, there's typically no cost.
The easiest way to control whether your iPhone uses the cellular network or Wi-Fi is to change the settings for individual apps. To do so, click the "settings" icon and choose "cellular." Scroll down to the list of apps, and turn off cellular data for the ones that you want to use only Wi-Fi. (In order to work, Wi-Fi must be turned on in the main settings menu.)
Which apps would you want to limit to Wi-Fi only? Those that potentially can use a lot of data, such as YouTube (video) or Pandora (music). But an e-mail or weather app that downloads little data could be allowed to use the cellular network.
Besides controlling whether apps use cellular or Wi-Fi, you can do the same thing with some behind-the-scenes activities of your phone. For instance, you can turn off cellular use for Apple's iCloud Drive service, so that your files will be backed up online only when Wi-Fi is available. You can also turn off cellular for an iPhone feature called "Wi-Fi assist." If left on, it automatically switches your phone from Wi-Fi to cellular if your Wi-Fi signal becomes weak as you move from one place to another. You can turn off iCloud Drive and Wi-Fi Assist by scrolling down below the app list described above.
