Mahjong can be played at 247mahjong.com and 247games.org. Both offer Mahjong free of charge, through a web browser and supported by advertisements. 247games.org offers apps for both Android and iOS.
247games.org offers 14 different Mahjong themes including Solitaire, Christmas, Summer, New Years and Cinco de Mayo. All themes are functionally the same with the only differences being the pictures on the tiles and background images. 247games.org also offers games such Solitaire, Bridge and Hearts.
247mahjongg.com specializes in Mahjong. While there is only one theme, different versions of the game are available with tile layouts that include, Hourglass, Sailboat, Diamond, Plus Sign, Arrow, Flag, City and Decuple.