Why does my iphone 5c buffer?

I have full bars and full Wi-Fi. But sometimes YouTube videos will buffer, vine videos will take forever to load and some Instagram pictures won't even load. Even tho I have full bars.

It happens

Your internet might not be fast.

The amount of bars you have + coverage doesn't really have anything to do with Instagram. Yes, it definitely has something to do with your YT videos but Instagram and YT are both on separate servers. This means that if too many people are trying to use Instagram and YT at the same time, the server will time out and have to restart in order for you to do anything. Usually buffering is the server's way of saying, "Hey, I know you want to watch this awesome video but I have to go out to the web and collect all the data I can about it before I can let you view it. If I don't collect any data it's basically like having an invalid link!"

Not to mention, if you're using LTE in a not-so-well-covered zone… The buffering time is going to be a lot longer vs a metro/city area because the server is used to having tons of people in the city get on all at once.