There was a viral tweet by UNO's official twitter page:
This got a lot of backlashes and many people still allow +2 stacking. But is there any official historical evidence to support either side before this tweet?
Draw card stacking is not part of the basic Uno game rules, but it is a house rule used so frequently that Mattel have included it in the bundled rules as a variant called "Progressive Uno".
The Progressive Uno rules are as follows:
Same rules as UNO® card game, except:
- When a player plays a Draw Two card, the next player may play another Draw Two card, causing the next player to draw 4 cards.
- Same rule applies to Wild Draw Four cards: When a player plays a Wild Draw Four card, the next player may play another Wild Draw Four card, causing the next player to draw 8 cards. The last player to play a consecutive Wild Draw Four card calls the color to continue play. If a Wild Draw Four card is played illegally and the player is challenged, the usual rules apply (See FUNCTIONS OF ACTION CARDS), except that the penalty will increase depending on the number of cards played.
- Players can continue to play consecutive Draw Two or Wild Draw Four cards, as long as they have them in their hands. For example, if 4 players in a row played Draw Two cards, the next player (who doesn’t have a Draw Two card) would have to draw 8 cards.
- You can only play one Draw Two or Wild Draw Four during your turn, even though you may have multiples of these cards in your hand.