.io arena

.io arena games are a style of casual action MMO game which features large, perpetual arenas which players can join into at any time. The gameplay within .io arena games is usually simple, such as collecting pick-up items like dots or food, which increases a player's score and their ability to overtake other players. Combat is generally very simple, with the victor usually being able to gain more power proportional to the opponent defeated. .io arena games also tend to show the player a leaderboard featuring the current most powerful players in the arena.

The genre rose to prominence with the release and viral success of Agar.io in 2015. In the following years, other developers would create games combining the base concepts with other simple score-based arcade-style gameplay mechanics, like Slither.io (2016) with snake gameplay and Splix.io (2016) with grid capture gameplay.

Note: while the popularity of .io arena games has inspired many developers to use the .io domain extension for any type of multiplayer web game, not all of these are .io arena games. If a game is built around lobbies with distinct matches, rounds, and winners, it should not be considered an .io arena game, and may instead fit better under another genre (most frequently battle royale).