To resign a game, you need to open the game that you wish to resign and then press the More icon (three white horizontal lines).

Tap the "Resign" option with the white flag icon.

Confirm your desire to resign.

Another rule is, if your opponent does not make a move soon, then the game will be automatically resigned for you.

The auto-resign times are as follows:
  • Games where it’s your turn will end after 45 days.
  • Games where it’s not your turn will hide from the ‘their move’ list after 14 days and will end after 45 days.
  • This is the same for both friends and instant play opponents.
  • While this will resign a game, it will also automatically create a new one.
  • In this case, if the player does not want to continue playing that opponent they need to go into the new game and do the same action but click decline instead.
Games that are inactive past these time limits will be auto-resigned by the game server. Resign option will only be available if it's your turn. If you are unable to resign since you're waiting for your opponent's move, but would like to remove a pending match. You can check this article.