Coin

Coins (also known as Bird Coins) are the main game currency that appears in almost every games of the Angry Birds series. They were first introduced in Angry Birds Friends, and then coins were featured in other games by later updates. For Bird Coins, they appear as small gold coins with Red's face on them. Some coins have different appearence in other games.

Angry Birds Friends
When you start the game for the first time after the release of the Bird Coins, you get a text box telling you about them, and you can also get 440, but only once. You can earn more for free by earning stars in Weekly Tournaments, and completing them. When you complete a Tournament Level, you will get 2 for,  4 for , and  8 for , if you get all the stars in a level, you will get  14. You can also get from daily rewards. You will get 4 in the first day,  6 in the second day in a row,  10 in the third day in a row,  16 in the fourth day in a row, and  50 in the fifth day in a row. However, streak will be restart every five days if you login every day.

Angry Birds Go!
In Angry Birds Go!, Bird Coins appear in every track and can be collected to increase the amount of awarded coins when finishing a race.

In v1.0, they are mainly used to purchase upgrades for the player's karts, but once the player unlocks Rocky Road, they can also be used to purchase new karts as well.

In v2.0, they are mainly used to purchase upgrades for the player's karts with upgrade parts, and it's also used for purchase 3 upgrade parts at the shop (100 coins for regular parts, 1,000 coins for Rare parts, and 10,000 for Epic parts). There's a big coins appear in every track as well, for 50 coins.

Angry Birds
Bird Coins are so far only appears in Angry Birds for Kakao. They used to purchase Power-Ups and Mighty Eagle. You can earn them by getting stars just for 10 coins.