Uno: questions and answers

Short answers to the questions people ask most about Uno. Everything else is in the full rules.

Can you stack draw two cards in Uno?
Not by the official rules. A draw two makes the next player draw two and miss their turn, and they cannot pass it on by playing a draw two of their own. Stacking is one of the most common house rules, so agree on it before the first deal.
When can you play a wild draw four?
Officially, only when you hold no card of the colour in play — cards of the same number or symbol in other colours do not count. The next player may challenge it. If you broke the rule, you draw four instead; if you did not, the challenger draws six.
What happens if you forget to say uno?
If another player calls you on it before the next player starts their turn, you draw two cards. Once that turn has begun, you are safe.
Can you finish on an action card or a wild?
Yes. If your last card is a draw two or a wild draw four, the next player still draws, and those cards count when the hand is scored.
Can you play a card you have just drawn?
Yes, as long as it can be played. If you cannot play, you draw one card, and if that card fits you may put it down straight away.
What does a reverse do with two players?
It works as a skip: the other player misses their turn and you go again.
How does scoring work in Uno?
The player who goes out scores the cards left in everyone else's hands: number cards at face value, skips, reverses and draw twos at 20, and wilds at 50. The first to 500 wins.
How many cards are in an Uno deck?
108: four colours with one zero, two of each number from one to nine and two each of skip, reverse and draw two, plus four wilds and four wild draw fours.