There are some pitfalls when it comes to data usage. Data charges can add up quickly, especially when tethering. I write this from the perspective of a MacBook, iPhone and iPad user, which uses those devices heavily and interchangeably.

Habits Which Need a Lot of Data

  • Updating iOS apps in iTunes on macOS. I have about 140 apps for iPhone and iPad. Those get automatically downloaded to iTunes on macOS when the device is synced with iTunes. They won’t be deleted automatically if the apps get deleted from iOS devices. Manually updating those uses a significant amount of data. If 20 apps get upgraded and a single app is 50 MB, 1 GB of data is used to update those apps. (They are only come to use if the iOS device is restored from backup while being connected to iTunes or the app has been removed from the App Store. Then the apps won’t be downloaded from the iTunes store but from local iTunes on this computer.) Mayor apps like Facebook, LinkedIn, Skype etc. are most likely bigger and weigh 80–100 MB.
  • Watching YouTube a lot or downloading movies and TV shows. Well, no surprise. Video uses a lot of data. The higher the video resolution and the longer the video, the higher the data.
  • Video chat. It’s video, see above.
  • Streaming music. A high-quality music stream (256 Kbit/s) uses about 2 MB per minute and 112.5 MB per hour. So nine hours of music streaming uses about 1 GB of data.
  • Audio books. Audio books are like music. A high quality audio book (128 Kbit/s) uses half of what high-quality music does.
  • Online and iCloud backup. iOS devices get automatically backed-up daily if connected to power, locked and being on Wi-Fi. The next backup size can be seen at Settings > General > Storage & iCloud Usage > iCloud Manage Storage > (The current device) > Next Backup Size. But these numbers change daily depending on what has changed on the device.
  • iCloud Photo Library. If enabled this will upload all photos and videos shot by this device to iCloud so they can be synced to different devices and are effectively backed-up. Depending on the amount of photos and videos shot on a day, these can add up to hundreds of megabytes or even gigabytes. Uploads are only done when on Wi-Fi.

Habits Which Use a Medium Amount of Data

  • Text messaging while sharing images and videos in this chat. Images use a couple of megabytes each. Videos use much more, likely dozens to hundreds of megabytes.
  • Email having attachments. Attachments can be large, up to the tens of megabytes. Images in emails are either attachments or have to be downloaded from the internet while viewing.
  • Web pages. Web pages can be small, because it’s just text. But most web pages have many images, fonts, styling, scripts which add useful behavior, and tracking and ad scripts. Fancier web pages start at 1 MB per page and can go to 5 MB. Homepage use more data than article pages. Scrolling down a long homepage may load data in the background, which can multiply the amount of data used for this page if scrolled long enough.
  • Maps. Maps use a medium amount of data. If you use maps for navigation and drive and hundreds of kilometers or miles, data usage can add up to hundreds of megabytes. Traditional navigation app have offline map data so they don’t have to use any data to display the route.

Habits Which Don’t Need a Lot of Data

  • Text messaging. Text uses a negligible amount of data compared to other formats. If you attach images and videos the amount of data increases massively.
  • Email without attachments. Emails without attachments and images are mostly text. See Text messaging.
  • Notifications. Notifications are very small amounts of text.
  • Location data. Location data uses a very small amount. See above if you use maps.
  • Background updates. In general they don’t use a lot of data if the app is conscious about data usage.

Things Eating Your Data Allowance You Don’t Know of

  • Automatic app updates. Automatic app updates run in the background on iOS and, if enabled, on macOS. They only run on Wi-Fi, but Macs can be tethered and won’t know about the phone using mobile data. Updates on iOS are much more frequent. It’s also likely that most people have more iOS apps than macOS apps, because they are cheaper and big companies have to have mobile apps, but get away with having just a website on desktop, like Facebook. An average non-gaming iOS app may be 50 MB in size, gaming apps are in the hundreds of megabytes. Some apps like Facebook, Facebook Messenger or TripAdvisor for example are updated every two weeks. And they are 80–100 MB in size. At least iOS only downloads changes and not the whole app again.
  • Podcast subscriptions. If you enabled automatic downloads of new podcast episodes on mobile and didn’t restrict it to only download on Wi-Fi, you may download a lot of data. This depends on the amount of subscriptions and updates to those. Podcasts use a quarter to half of what music uses. But they are much longer than the average song.

Bottom Line

The bottom line is simple: Video, music streaming and app updates use the most data. The rest depends on your usage pattern and frequency. This is no surprise, but sometimes it’s hard to understand for what the data has been used for. And hopefully in the near future mobile data plans will have much more data included for a reasonable price. Then only video and excessive music streaming will be an issue.