To be the best at Uno Online you must pay attention to your opponents. Always keep in mind the numbers of cards they have in their hand and the cards they are playing. Save letters 2 and 3 for emergencies. Don' t play them too early, you may need them in case an opponent is going to run out of cards. Also, you need to get rid of the high cards first. In case of losing the game, the high cards will give more score to the winner of the game. If you get the chance, change the color frequently. Use action cards wisely, they can change the course of a game even if you lose.