Mancala is a game that's been around since 500 AD. The reason why it's persisted through all of these years is simple: it's a fun, challenging brain game that can be played at all ages.

Mancala.playdrift.com
Mancala.playdrift.com, in our opinion, is one of the best options you can get for online Mancala play. Why? Because it allows you to play with other online players instead of just against a computer.
Cool Math Games
This is another free website where you can play Mancala along with other math centered games like Sudoku and 2048. Cool Math Games' version of Mancala makes it clear whether it's your turn or the computer's turn.
Two Player Games
Two Player Games offers up a bit of a twist on the classic Mancala board that the other sites we've mentioned offer. Instead of the classic rocks or beads, this version uses snails as your playing pieces.