S4 League is a third-person shooter MMO (Massively Multiplayer Online) game. The four „S” from the title stand for: Style, eSper, Shooting and Sports. The game is a combination between a shooter and a sports simulator, with 3D anime graphics and techno soundtrack.

The game has no background story. Players just connect to a virtual world where they have to prove their skills while advancing through all the 100 levels (Beginner, Rookie, Super Rookie, Semi Pro, Pro, S1, S2, S3, S4 - Master), based on the amount of experience points they have gathered after each game played. The player can create up to three characters of either gender. Before players can start a game, the character must have equipped at least one weapon and one skill. Players can choose between close-range, mid-range, long-range (sniping), mental, throwing, and support weapons. Players can also choose between active or passive Skills.

Costumes, items, weapons and skills can be bought from the game shop with PEN or AP. PEN is virtual money, earned by playing matches, while AP is earned by paying real money (multiple methods, from credit cards to mobile text messages, specific to each country). Costumes, items, weapons and skills can be permanent or rented (hour-based or day-based). Permanent stuff needs repairs after each use, rented stuff doesn't. Day-based items follow the real life time, while hour-based items count only when playing.

After players create and equip their characters with items purchased from the shop, they are ready to join a server based on country/language, and then join a room based on Game Mode. A room can have maximum 12 players connected: 6 players in Alpha Team and 6 players in Beta Team.

There are various modes in the game: In Touchdown Mode , the most played game mode, players must take a yellow, bouncing ball called "fumbi", run with it to the other side of the map and put it in the red goalpost. Fumbi can be carried by multiple teammates along the way.

In Deathmatch Mode, players must kill each other in order to take their team to victory before the time ends.