The Exp. Share is a held item introduced in Generation II (Exp. Share in Generation I existed but was not a held item and divided exp amongst your entire party). However, in Generation VI the Exp. share was changed back to its original form.
Info
When the player gives an Exp. Share to a Pokémon in their party that isn't first in the lineup and battles, part of the experience points gained by the battling Pokémon is given to the one holding the Exp. Share. However, the Pokémon who is battling does not gain the regular amount of experience; it gains half of the normal amount. There is usually only one Exp. Share found in each game; however, you can get more than one by cheating, winning one at the lottery, trading Pokémon holding another Exp. Share, or, in Pokémon Black and White, receiving a second one from the Pokémon Fan Club Chairman.
Any Pokémon actively in the battle receive half of the total experience. The other half gets split up among any Pokémon holding Exp. Shares. Example:
| Opponent | Gives | Battling Pokémon | # of Pokémon with Exp. Share | Battling Pokémon receives | The Pokémon with Exp. Shares receive |
|---|---|---|---|---|---|
|
100 Exp. points | 
|
2 | 50 Exp. points | 25 Exp. points |
From Generation VI onwards, the Exp. Share returned to being a key item that shares 50% of the Exp earned in battle with any Pokémon that are in your current party and did not join the battle. However, this can possibly be remedied if only one Pokémon participated in the battle and was holding a Lucky Egg, since they multiply Exp by 150%.
If the Pokémon that is holding the Exp. Share is the one fighting, extra experience is not gained and experience is not given to any of the other Pokémon in the party. The only item that raises the amount of XP gained is the lucky egg which can be found rarely being held by a wild Chansey.
In Generation VI, Pokémon, who win a battle will receive 100 percent on the XP, and the rest of the Pokémon in the party will only receive 50 percent, rather than splitting all of the XP to the party.
Locations
- Gold, Silver, and Crystal: Give Mr. Pokémon the Red Scale from the Red Gyarados.
- Ruby and Sapphire and Emerald: Given by Mr. Stone in Rustboro City after the player has given his letter to Steven Stone.
- Diamond and Pearl, Platinum: Given by Professor Rowan"s assistant in the gatehouse south of Eterna city if the player has seen 35 Pokémon.
- X and Y: Given by Alexa after defeating the 1st gym in Santalune City.
- Omega Ruby and Alpha Sapphire: Given by a man after the player rescued him from either a Team Magma Grunt or Team Aqua Grunt in Petalburg Woods.
- Sun and Moon: Given by Professor Kukui at Route 1.