What uses data on an iPhone?

So I just got my iPhone, and I have a 1GB Family Share Plan with my dad. He said to be careful about going over the data limit, or Verizon would end up charging us extra… So what uses up the data on the phone? I know that if I'm connected to wi-fi it won't be affected, but if I go on Safari or YouTube using 4G, how much will it take? Can someone tell me what exactly effects the phone's data usage?

It really depends…
One YouTube video can take anywhere between 5mb-100+mob depending in the quality and length

For safari… One web page may only take 15kb to load… But another may take 100+mb to load… Depends on what the page has… How many images, the quality of images… Etc

As for other things… Anything that may give you notifications… Email app, Facebook… Etc, even when you are not using them thy run background checks… But these checks usually never exceed over 2mb a day… But sometimes something goes wrong and it just keeps checking

Anything done using 3G will use data.

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