During the game it might happen that unknown words are placed. Scrabble3D offers three alternatives to check words beginning with a simple game for training purpose up to tournament rules. In any case the validation is done first by the computer based on the dictionary; unknown words are not necessarily invalid. It might be unknown for the computer because it's a very long word, for example. And therefore the word can be confirmed anyway after the first validation.
If you activate the option Takeback, the current player is informed in case of unknown words. She decides to place another word or to continue with the poll.
First it's checked if the dictionaries of all connected players contain both the placed as well as every connected words (in local games it's of course just one dictionary). In case a word is not found at any dictionary, the move is placed into the confirmation poll. That means all players decide about the validity. If all players confirm the placed words are treated as valid, but if only one disagrees the move is rejected.
The validation is not done automatically in tournaments. You rather have a certain period (usually a few seconds) to object the move and to start the validation procedure. In Scrabble3D this is done by clicking the toolbar button challenge (you can use also the menu or press ctrl+H); the first click is being evaluated in case more than one player wants to object the move. The procedure then runs according the poll: first the check is done silently and only if one word is unknown for any player the confirmation poll is shown.
Additional to the common penalty that is given to the objecting player in case when all words are actually valid, you can receive an equivalent bonus for approved objections. Of course the score for invalid moves is set always to zero.
CLABBERS, an anagram of SCRABBLE, allows to play words with scrambled letters. The validity check tests not only the word itself but as well any permutation of letters. In real games the player has to specify which word is constituted by the anagram - this does not apply here. The increased ability to play parallel to pre-existing words makes for much higher scores.