A free app for Android, by Zynga.
Play Rummy Plus -Live Online Rummy Game on Facebook Messenger for free. No registration or sign-up required. The game is played with real players from around the world and is totally free. There are different games modes, some of them free. Some of them require purchase, and others are for entertainment purposes only. The most common rules are:
You must be an adult to play.
You cannot change the cards after the first hand is dealt.
You must follow suit. If you don’t have the card in hand, you must draw a card from the deck.
You can either play online with real players or offline with bots.
You can play with friends or with strangers.