FreeMahjong.org provides an online version of the classic Mahjong game. Additionally, 247Mahjong.com provides a classic version of the game, plus a wide range of layouts with varying difficulty levels; these include "Butterfly Mahjong," "Mahjong Circles" and "Double Play Mahjong."
MahjongGames.com offers classic Mahjong with 60 levels, plus numerous alternative styles and versions of the game. As of July 2015, some of the top-rated versions on MahjongGames.com include "Castle Mahjong," "Mahjong Dark Dimensions," "Hex Mahjong" and "Opposites Attract."
AGame.com offers "Mahjong Quest," in which players can choose to go North, East, South or West and then progress through the increasingly harder levels.