.io Game

A .io Game is a genre of video game that originated in the late 2010s. These games, belonging to the MMO (massively multiplayer online) genre, are defined by having most of the following traits:

1. Quick and easy to join: .io games don't require the creation of an account to play (although some do offer the option); you simply enter your username and go. They are also often browser-based, not requiring any downloads aside from the plug-in used to run the game, making them even simpler and quicker to join. Many also offer mobile apps, allowing them to be played on the go.
2. Simple rules: Quite often, one can instantly deduce how to play simply by seeing the game screen. Other games show a quick tutorial to explain a few additional nuances, but it should take one less than a minute to grasp the basics.
3. Player Versus Player: .io games pit you against other players, whether it be in a free-for-all or team-based competition.
4. Power growth: Players grow more powerful as they play. A player's power level is often represented by his character growing larger. However, being eliminated often means losing most or all of that power.
5. Gameplay over story: the vast majority of such games have no storyline at all. Only a few games hint at a backstory, like Surviv.io with its change log notes and brief and well-hidden audio recordings, or BattleRoyale.io with the Flavor Text in its Monster Compendium.

The name of the genre is derived from the fact that many of these games' sites have the ".io" top-level domain, which was originally intended for sites related to the British Indian Ocean Territory but has since become popular with tech startups due to making a pun on input/output. In these cases, the "io" is treated as part of the game's name, with the "dot" being considered silent (Agar.io is pronounced "agario", not "agar" or "agar dot io").

The Trope Maker is Agar.io. Due to its simple yet addictive gameplay, it exploded in popularity and quickly became an internet phenomenon. Follow the Leader soon ensued when Slither.io reached similar popularity levels, and the genre was born.

---

Games in the genre include:

• Agar.io: The first .io game, and the first to gain widespread popularity. It is a Rising Up The Food Chain Game where players control a cell which can feed on both food particles found on the ground and smaller players, growing in size as they eat.
• BattleRoyale.io: An SF-themed game where players fight each other to the death on a failing research station, set on Jupiter's moon Io. Notable for its lightning system, and for including the most detailed backstory out of all .io games so far.
• Biters.io: A game where players control cartoony Biter creatures and brawl over a teatime table in a bid to become the largest, while healing with chocolate chip cookies and restoring stamina with water.
• Bloble.io: A tower defence game, where the players first build walls and turrets in rings around their fixed headquarters, then send out troops to attack each other.
• Deeeep.io: A side-view game that simulates a marine ecosystem, where players start off as Tier 1 clownfish or marine worms, eat food and/or each other and evolve into stronger creatures. Besides the sea and the titular deeeep, there are also ways to reach the swamp and the arctic, and even get to their surface. However, all species have their oxygen, pressure, temperature and salinity needs, and will take damage when venturing outside their comfort zone. Thus, its evolutionary tree gets wider as the players ascend it - while there are ~5 options at the lower tiers, tier 10 culminates with 24 options.
• defly.io: A game where players control helicopters and need to place down towers and connect them in order to control territory, along with attacking rivals' towers and each other.
• Devast.io: A game about survival and Item Crafting in a post-nuclear environment.
• Diepio: A top-down Shoot 'Em Up in which players control a tank. As you earn points by destroying neutral targets and other players, you can upgrade your tank's attributes and choose from several branching evolution paths, each with unique abilities.
• Doblons.io: A top-down game where the player controls an ironclad-era ship, and can upgrade it in many mutually exclusive ways by collecting the titular doblons and fighting other players.
• Driftin.io: A top-down racing game where the player controls one of eleven vehicle classes, and competes with other players to become the first to reach 20 laps without crashing, which resets their number of laps. Each vehicle can be upgraded through points earned by finishing laps or wrecking the other players.
• FacePunch.io: A top-down game about cartoony boxing, where players control various characters that can only punch with left or right gloves, and occasionally deploy their ultimates.
• Familiars.io: An MMORPG inspired by Pokémon in which you collect familiars which level up as they win battles and walk around an expansive open world battling other familiars as well as other players if the Player Vs Player option is on.
• Flaap.io: A game that takes Flappy Bird and makes it multiplayer. Players try to get through as many pipes as possible, as the game gets faster and the bird's appearance changes.
• FlyOrDie.io: A side-view game where players start off as lowly Flies that control little better than a Flappy Bird, and are tasked with evolving into first stronger insects, then graceful birds, then a variety of increasingly fantastical creatures, until they potentially end up as a practically invulnerable Grim Reaper. The game also includes a variety of non-player-controlled creatures in a nearly complete simulation of an ecosystem.
• Foes.io: A top-down 2D game set in an abandoned military base, and centered around smaller-scale battle royale-style matches that cap at 30 players.
• Goons.io: A game that has players control small creatures holding swords or other close range weapons and try to hit each other with them. Successful kills result in getting your weapon bigger until it reaches a certain length.
• Hexagor.io: A Real-Time Strategy game, where players click on hexes to take them over in a bid to control 500 of them, while trying to protect their territory and avoid getting their capital captured.
• Hexar.io: In this game, players control snakelike creatures that have to surround a hexagonal grid, make it their color, and make sure their trails aren't touched by other players.
• Hordes.io: An MMORPG where practically every character and enemy is a cube with limbs of various sizes.
• Karnage.io: A top-down 3D shooter set in a Quake-style futuristic arena where practically everyone uses a grenade launcher in addition to the conventional weapons. Features classes from Vertix.io
• Krunker.io: A 3D First-Person Shooter that is a successor to Vertix.io and Karnage.io, from the creator of both. It is essentially a browser-based equivalent to Counter-Strike, which replaces weapon shop with a dozen of preset classes, as well as a more fast-paced, arcadey gameplay with Quake-style movement. Also features a map editor and a variety of custom game modes.
• Land-io: A top-down game in which players encircle regions of the board to claim them as their territory.
• Thelast.io is a 2D top-down battle royale game with a fantasy theme, where the only gun is a slow-firing blunderbuss, but there are plenty of melee weapons and magic staffs to deploy instead.
• MassiveMatch.io: A swapping Match-Three Game where everyone plays simultaneously on the same board. Rotates between several different cooperative and team-competition modes, though they all track individual scores as well.
• MiniGiants.io: A top-down multiplayer game where each player picks a character and starts off small, but gets larger as they gain levels, and soon turns into a real giant.
• MooMoo.io: A browser-based survival game, where the player has to gather resources and fight the animals and other players to survive in prehistoric times.
• Mope.io: A significant evolution of agar.io, which keeps the movement mechanics, but places players into real ecosystems as (mostly) real-world animals that all have a special ability or two, then forces them into predator-prey relationships where eating is necessary to evolve into the next animal tier, along with drinking water just to survive.
• Narwhale.io: A game in which players control a narwhal, and must skewer other players on their horn. Each kill rewards you with an upgrade to your attributes such as speed or dash cooldown.
• Nightpoint.io: A top-down game where players become survivors in a town taken over by infinite hordes of zombies, and can either fight each other for dominance in the Free for All mode, or bundle into two teams in Capture the Flag mode.
  • Has a Battle Royale spin-off named Battlepoint.io, which functions very similarly.
• Pikes.io: Players control a square character holding a pike. The objective is to kill others with it, which makes it longer and easier to keep killing.
• Shooters.io: A space combat game where each player controls a fleet of triangular spaceships, which immediately grows as it destroys/takes over the ships in the enemy fleets with their beam weapons. Players are defeated only when they lose all of their ships.
• sl4sh.io: Players control a cursor, which can perform a Dash Attack to slash other players or use a reflector shield to protect oneself. There are various classes available, and killing enemies and neutral beings or picking up energy orbs increases one's level, allowing various types of upgrades to be picked.
• Slither.io: Basically a multiplayer online version of Snake. Players control a snake which becomes bigger and longer as it feeds on energy pellets, and must avoid bumping into other players (which kills you instantly) while trying to make others run into them (which turns their body into food).
• Smashers.io: You control cartoony fighters trying to smash each other with ridiculously large hammers, and who can gain extra points by whacking moles and an invulnerable Sand Worm present around the map.
• Spinz.io: This game has players control fidget spinners that collect orbs to spin faster and kill slower opponents. Being four times as fast as your opponent will be enough to kill them instantly.
• splix.io: A multiplayer version of Qix. Players start with a small patch of land, and must capture more by drawing a closed shape over unclaimed or enemy territory, but being bumped into while outside of your home turf kills you.
• Starve.io: A prehistoric survival game with cartoonish graphics, agar.io- style gliding movement, focus on Item Crafting, and a complete lack of ranged weapons.
• Surviv.io: A top-down battle royale inspired by Player Unknowns Battlegrounds. Around 80 players spawn on an island and must scavenge weapons and items in order to defeat all others and be the last man standing.
• Swordz.io: This game has players fight each others with swords. Getting a multiple of 100 experience will result in a level up and a longer sword.
• Vertix.io is a 2D top-down shooter which features 10 classes (which later reappeared in 'Karnage.io and Krunker.io''), multiple individual and team-based game modes, and a wide variety of cosmetic items awarded at the end of the match.
• Wanderersio: A pixel-art style, 2D top-down game (by the same maker of Wilds.io) where you control a tribe across a hostile sandbox of other tribes and non-playable barbarians by guiding them to objects that they'll interact with if the tools are available. Tribes of the same color can work together in sharing resources and taking down other tribes.
• War Brokers: A 3D first-person shooter game with battle royale and team vs. team game modes.
• Wilds.io: A 2D top-down game with pixel-art graphics, where player controls a Viking-era character and fights with others in 1v1 Arena, 2v2 "Browars" or large team-based Desert Fort/Winter Survival modes, which also include non-playable characters. The game is focused on a complex combat system, which has blocks, parries, kicks, dashes, dodge rolls (which will also knock enemies over), and several melee and ranged weapons, along with items like grenades, bombs and potions.
• Wings.io: A Shoot 'Em Up similar to Luftrausers: players pilot a fighter plane, and must shoot down enemy players. The plane is armed with a machine gun by default, but other weapons can be picked up including a shotgun, laser cannon, and homing missiles.
• Zlap.io: A game in which players have maces and must kill other players with them. Successful kills will make it bigger and easier to hit and defend yourself with them.
• Zombs Royale.io: A top-down, browser-based equivalent to Fortnite. A 100 players or so disembark from a plane over an island, find loads of weapons inside crates and must kill each other until a survivor emerges, while the island is being flooded with poison gas.

---