Level

Level, simply put, is how powerful you are. The higher your level is, the more damage you will do with magic and physical attacks, your defense, HP, and MP will increase, and you will learn more spells to cast.

To level up, you must gain experience. Experience is gained by defeating enemies, unless the form or situation you are in requires a different method. Each game rewards leveling up differently.

Leveling up
Listed below are all the rewards you can get for each individual game. This includes level up rewards for not just Sora, but also Donald and Goofy except where noted.

Kingdom Hearts

 * 1) Increase in Health Points.
 * 2) Increase in Magic Points.
 * 3) Increase in Strength.
 * 4) Increase in Defense.
 * 5) Increase in Ability Points
 * 6) Gain a new ability.
 * 7) Increase in accessory slots.
 * 8) Increase in item slots.

Kingdom Hearts: Chain of Memories
In Chain of Memories, the player is presented with three choices upon leveling up. The choices available depend on whether that option has been selected in the past and whether Sora or Riku are being played.

Sora

 * 1) Increase in HP.
 * 2) Increase in Card Points.
 * 3) Gain a new Sleight.

Riku

 * 1) Increase in HP
 * 2) Increase in Attack Points
 * 3) Increase in DP, or Darkness Points.

Kingdom Hearts II
In Kingdom Hearts II the only way to gain HP, MP, and certain abilities is to defeat bosses, which hugely differs from the other games in the series.
 * 1) Increase in Strength.
 * 2) Increase in Defense.
 * 3) Increase in Magic (Only Sora and Donald)
 * 4) Increase in Ability Points
 * 5) Gain a new Ability.

Kingdom Hearts 358/2 Days
In Kingdom Hearts 358/2 Days, although a level is gained each time enough EXP is amassed, Roxas does not actually increase in level at that point. Instead, he automatically obtains a Level Up panel, which increases his level when installed into a panel slot or by itself. There are also link panels that double, triple and quadruple the levels gained from the LV Up panels linked to them.

Bonus Level
Bonus Levels are rewards that are only received in Kingdom Hearts II, because no experience is gained from bosses. Sora, Donald, Goofy and (if applicable) a fourth party member will receive a Bonus Level after a boss fight in Kingdom Hearts II. All magic spells received are for the entire group, but some abilities are exclusive to certain characters.

Kingdom Hearts

 * 1) A new spell or upgrade to it.
 * 2) A new Ability.
 * 3) A new Accessory.

Kingdom Hearts II

 * 1) Increase in Health Points.
 * 2) Increase in Magic Points.
 * 3) More armor slots.
 * 4) More accessory slots.
 * 5) More item slots.
 * 6) A new spell or upgrade to it.
 * 7) An extra Drive Gauge. (Only Sora)

Form Level
Every form (except for AntiForm) has a separate level, which experience for is gained by different means than the regular form's "kill enemies" rule, and can only be gained if the conditions are fulfilled while in that form. At levels 3, 5, and 7, you get an upgrade to that Form's Growth ability and to Sora's growth ability corresponding to the same form (at level 3 you gain the ability, 5 and 7 upgrade it). Forms can have Growth abilities up to Max Level, and regular Sora can only have it up to level 3.

You also gain an ability for Sora when the Form Levels up to levels 4 and 6, and is in most cases the only way to get them. These abilities are added to Sora's regular abilities list. In every level, you also gain a Form Gauge upgrade which increases the time Sora can remain in a Drive Form.

Kingdom Hearts
There is no way to level up your summons in Kingdom Hearts, but you can increase the amount of time the stay on the field by equipping the Cheer ability to Sora, Donald, and Goofy.

Kingdom Hearts II
In Kingdom Hearts II, Summons can be leveled up by using any one of them. You earn one summon experience point for every Summon Gauge bar that is consumed during a summon. Once enough points are gained the Summon Gauge increases so summons can stay out longer.