Difficulty is an option in some single player/co-op modes that allows a player to adjust the game after one's skill. In the most cases, there are five difficulty levels. Depending on what mode is being played, different difficulty levels will affect the game in different ways. For example, a higher difficulty level in the Subspace Emissary will make the enemies harder by giving them more HP and making their attacks stronger, while a higher difficulty level in Target Smash won't affect the characters' properties at all, but instead change the stage's design into a more difficult one. Sometimes, unlockables such as trophies or stickers depend on the difficulty on which a game mode is cleared. In the Subspace Emissary, Stock Balls vary in number, from appearing in most levels in Easy to never appearing in Intense.
In Smash 64, the difficulty setting is only available for the 1P Game. In the other two games, the setting appears for the Classic Mode, Adventure Mode/Subspace Emissary and All-Star Mode. Additionally, in Brawl, the setting is available for the newly added mode Boss Battles, and has been added to Event matches and Target Smash!!. However, on the event matches in Super Smash Bros. Brawl, there are three difficulties (Easy, Normal, and Hard).
In Event Matches, only three difficulty levels are available: Easy (blue difficulty), Normal (green difficulty) and Hard (yellow difficulty).
It's being revealed at the E3 that, at least, Super Smash Bros. for Nintendo 3DS will include an intensity system similar to the of Kid Icarus: Uprising. As with placing hearts on the Fiend's Cauldron from the latter game to increase or decrease the difficulty, players will be able to place gold coins on a scale from 2.0 to 9.0 values (and lower to 2.0 to 0.0 values) to increase or decrease the difficulty of a currently unknown game mode. At least three of the intensities' names are the same as Kid Icarus: Uprising: