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 x440, 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 x2 for,  x4 for , and  x8 for , if you get all the stars in a level, you will get  x14. You can also get from daily rewards. You will get x4 in the first day,  x6 in the second day in a row,  x10 in the third day in a row,  x16 in the fourth day in a row, and  x50 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.

Bad Piggies
In Bad Piggies, the player earn coins by completing a level, get the Star Boxes (only in Sandbox), and feed the King Pig. The players can get coins by earning stars. Player get 1 coin for 1 star, 2 for 2 stars, and 3 for 3 stars.

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.