Android vs iOS on smartphones – worldwide statistics

Today Android is the most polular operational system for smartphones in the world.

The graph below is showing the number of mobile phone users by operational system in the world.


Android users worldwide

As you can see, Android is the most popular operations system for smartphones with over 1 billion users in the world, which is over 81% off all mobile users on Earth.


It is obvious that iOS is not so popular as Android.
What do you think why?