The aim of the game is to be the first player to score 500 points, achieved (usually over several rounds of play) by being the first to play all of one's own cards and scoring points for the cards still held by the other players.
The 2018 edition of the game consists of 112 cards: 25 in each of four color suits (red, yellow, green, blue), each suit consisting of one zero, two each of 1 through 9, and two each of the action cards "Skip", "Draw Two", and "Reverse". The deck also contains four "Wild" cards, four "Wild Draw Four", one "Wild Shuffle Hands" and three "Wild Customizable".Sets manufactured prior to 2018 do not contain these last two types of Wild cards, for a total of 108 cards in the deck.
For each hand, a dealer is determined by having each player randomly draw one card from the deck. The player with the highest number card deals, and all cards are reshuffled into the deck to begin the dealing.
To start a hand, seven cards are dealt to each player, and the top card of the remaining deck is flipped over and set aside to begin the discard pile. The player to the dealer's left plays first unless the first card on the discard pile is an action or Wild card (see below). On a player's turn, they must do one of the following:
- play one card matching the discard in color, number, or symbol
- play a Wild card, or a playable Wild Draw Four card (see restriction below)
- draw the top card from the deck, and optionally play it if possible
Cards are played by laying them face-up on top of the discard pile. Play initially proceeds clockwise around the table.
Action or Wild cards have the following effects:
| Card | Effect when played from hand | Effect as first discard |
|---|---|---|
| Skip | Next player in sequence misses a turn | Player to dealer's left misses a turn |
| Reverse | Order of play switches directions (clockwise to counterclockwise, or vice versa) | Dealer plays first; play proceeds counterclockwise |
| Draw Two (+2) | Next player in sequence draws two cards and misses a turn | Player to dealer's left draws two cards and misses a turn |
| Wild | Player declares the next color to be matched (may be used on any turn even if the player has matching color) | Player to dealer's left declares the first color to be matched and takes the first turn |
| Wild Draw Four | Player declares the next color to be matched; next player in sequence draws four cards and misses a turn. May be legally played only if the player has no cards of the current color (see Penalties) | Card is returned to the deck, then a new card is laid down into the discard pile (deck may be reshuffled first if needed) |
- A player who draws a playable card from the deck must either play or keep that card and may play no other card from their hand on that turn.
- A player may play a Wild card at any time, even if that player has other playable cards.
- A player may play a Wild Draw Four card only if that player has no cards matching the current color. The player may have cards of a different color matching the current number or symbol or a Wild card and still play the Wild Draw Four card. A player who plays a Wild Draw Four may be challenged by the next player in sequence (see Penalties) to prove that their hand meets this condition.
- If not otherwise challenged, an illegally played Wild Draw Four stays without penalty for its player.
- When playing a Wild or Wild Draw Four card, a player may declare the current color as the next one to be matched.
- If the draw deck runs out during play, the top discard is set aside and the rest of the pile is shuffled to create a new deck. Play then proceeds normally.
- It is illegal to trade cards of any sort with another player.
A player who plays their penultimate card must call "Uno" as a warning to the other players.
The first player to get rid of their last card ("going out") wins the hand and scores points for the cards held by the other players. Number cards count their face value, all action cards count 20, and Wild and Wild Draw Four cards count 50. If a Draw Two or Wild Draw Four card is played to go out, the next player in the sequence must draw the appropriate number of cards before the score is tallied.
The first player to score 500 points wins the game.
Penalties
- If a player does not call "Uno" after laying down their penultimate card and is caught before the next player in sequence starts to take a turn (i.e., plays a card from their hand, draws from the deck, or touches the discard pile), they must draw two cards as a penalty. If the player is not caught in time or remembers to call "Uno" before being caught, no penalty applies to that player.
- If a player plays a Wild Draw Four card, the next player in turn order may choose to challenge its use. The player who used the Wild Draw Four must privately show their hand to the challenging player in order to demonstrate that they had no prior matching colored cards. If the challenge is successful, then the challenged player must draw four cards instead and play continues with the challenger. Otherwise, the challenger must draw six cards – the four cards they were already required to draw plus two more cards – and lose their turn. In either case, the Wild Draw Four stays with its chosen color.