Happiness

Happiness is a number between 0 and 255 that gauges how friendly a Pokémon is towards its trainer.

Every Pokémon starts with 0 happiness, which will change based on certain events:

• Keeping the Pokémon outside of its Poké Ball will cause it to slowly gain happiness.
• Leveling up the Pokémon will raise happiness.
• Letting the Pokémon faint will lower happiness.
• Trading the Pokémon will reset its happiness to 0.
• Capturing a Pokémon in a Friend Ball will set its initial happiness to 200.
• Capturing the Pokémon in a Luxury Ball or letting the Pokémon hold a Soothe Bell will cause events that raise happiness to increase happiness by an additional one point each. These two conditions can stack with each other.

Evolution

A happiness of 220 or more upon leveling up is necessary to evolve:

• Golbat->Crobat
• Eevee->Espeon (day)
• Eevee->Umbreon (night)
• Pichu->Pikachu
• Igglybuff->Jigglypuff
• Munchlax->Snorlax
• Swadloon->Leavanny

Bugs

• A Pokémon caught with a Friend Ball will appear to have a happiness of 200 immediately after it is caught, but will revert back to 0 after gaining or losing happiness.