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.

Card Hunter
strategy / board game
Blue Manchu

Cut the Rope Time Travel
puzzle
ZeptoLab

Bit Heroes
RPG / MMORPG
Juppiomenz

FARA
RPG / roguelike
Brian Is Creative

atWar
strategy
atWar team

Samorost
adventure / point & click
Amanita Design

Tetris Fun
puzzle / tile-matching
zygomatic

The Settlers Online
strategy / MMORTS
Blue Byte Software

Torn City
RPG / MMORPG
Joe Chedburn

Hattrick
simulation / management
Hattrick Limited

Sextris
puzzle / tile-matching
Sextris

Circus Hidden Objects
puzzle / hidden object
zygomatic

Daily Crossword
puzzle
zygomatic

Battlestar Galactica Online
shooter / MMOFPS
Bigpoint Games

Imperia Online
strategy / MMORTS
Imperia Online Ltd.

8-Bit Bayonetta
action / run and gun
PlatinumGames

Progress Quest
RPG
Eric Fredricksen

There is no game
puzzle
Draw Me A Pixel

Travian
strategy / MMORTS
Travian Games

Bejeweled REMAKE
puzzle / tile-matching
szewczyk

Bloxorz
puzzle
DX Interactive