This means that if you have an iPhone, your friend has an Android phone and your brother has an iPad, you can all play together. Then, you can play as much as you like with no ads.
To play online with friends, you must all buy the Monopoly app which costs $3.99. The Monopoly app allows you to play Monopoly multiplayer on your phone or tablet.
Play Monopoly on your phone or tablet with the Monopoly app
