Browser based free games
Play free and free-to-play games designed to be played direclty in a browser (this includes both browser-based games and flash games)
Here are some of the best browser games you can play directly online: MMORPGs, collectible card games, strategy games and more. Browser games usually doesn't require nothing more than an updated browser (Chrome, Firefox, Edge, Opera, etc.) and are playable on any PC or Mac. Some of them may require a Flash plugin.
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Therian Saga
RPG
Fatecraft

Battlestar Galactica Online
shooter / MMOFPS
Bigpoint Games

Epic Battle Fantasy 3
RPG / JRPG
Matt Roszak

Monster Slayers
action / brawler
Nerdook

Fairune
RPG / JRPG
Skipmore

Questionaut
adventure / point & click
Amanita Design

Supremacy 1914
strategy / wargame
Bytro Labs

Adventure Quest Worlds
RPG / MMORPG
Artix Entertainment

Lost Pig
adventure / interactive fiction
Admiral Jota

Imperia Online
strategy / MMORTS
Imperia Online Ltd.

Travian: Legends
strategy / MMORTS
Travian Games

Kingdom of Loathing
RPG
Asymmetric Publications

Popmundo
simulation
ExtraLives AB

Torn City
RPG / MMORPG
Joe Chedburn

Progress Quest
RPG / idle clicker
Eric Fredricksen

Star Wars Combine
RPG / MMORPG
SWC Programming Team

Hattrick
simulation / management
Hattrick Limited

123 Strip Poker
card game / strip poker
LimeSoda

247 Mahjong
puzzle / mahjong
Games LLC

Batheo
strategy / MMORTS
Clap Along

Bloxorz
puzzle
DX Interactive