Is "Mate Prevails" not an FIDE rule? I couldn't see it in the FIDE website but I heard about it from many players.

UPDATE: "Mate Prevails" is a claim some players make that they win the game after 'flag fall' if they can force a checkmate in one move.

  • 2
    For anybody who doesn't know "mate prevails". It's a situation that you make a checkmate move but as soon as you make it, your also lose on time. The poster is asking "Is this win for me cos I checkmated my opponent or I lose because I run out of time?".
    – SmallChess
    Apr 9, 2015 at 6:10
  • 1
    Mate on the board prevails, if you don't make the checkmating move before opponent or arbiter notices and calls flag fall you've lost on time.
    – magd
    Apr 9, 2015 at 12:37
  • It seems that the trickiest situation is when in some player's turn their flag falls and they can mate in one in that very turn, or are in the process of doing it when their flag falls, or it is otherwise uncertain which occurred first. dfan's answer only addresses the situation where the flag falls after checkmate and magd's comment and answer seem to address the situation where the flag falls during their a player's turn while a mate in one is left on the board, which they have not exercised yet.
    – hkBst
    Feb 11, 2016 at 11:57

2 Answers 2


If you make a checkmating move before your flag falls, but then your flag falls before you press the clock, you win. The relevant FIDE rules (emphasis mine) are:

5.1.a. The game is won by the player who has checkmated his opponent’s king. This immediately ends the game, provided that the move producing the checkmate position was in accordance with Article 3 and Articles 4.2 – 4.7.

6.2.a. During the game each player, having made his move on the chessboard, shall stop his own clock and start his opponent’s clock (that is to say, he shall press his clock). This “completes” the move. A move is also completed if the move ends the game (see Articles 5.1.a, 5.2.a, 5.2.b, 5.2.c, 9.6a, 9.6b and 9.7).

6.3.a. When using a chessclock, each player must complete a minimum number of moves or all moves in an allotted period of time.

6.9 Except where one of Articles 5.1.a, 5.1.b, 5.2.a, 5.2.b, 5.2.c applies, if a player does not complete the prescribed number of moves in the allotted time, the game is lost by that player.


It's not a real rule in FIDE rules. Seems like an anachronism.

  • Would the downvoter care to explain? The answer is true and complete. The comment I made in the original question takes it a bit further.
    – magd
    Apr 9, 2015 at 12:53
  • dfan's answer indicates that FIDE rules do in fact address the issue. What rule is not real?
    – Daniel
    Apr 23, 2015 at 4:05
  • The rule saying that you win if it's mate in one after the flag drops (and is claimed).
    – magd
    Apr 23, 2015 at 8:31
  • i.e. In dfans example the mating move is in the process of being made while 'flag fall' occurs not 'able to be forced.. Also flag fall has not really occurred because it hasn't been claimed.
    – magd
    Apr 23, 2015 at 8:33
  • Your answer isn't clear enough, since the question isn't. I clarified OP's edit, but I think your answer would benefit from going into a bit more detail. I didn't downvote, but two people found it unhelpful.
    – Daniel
    Apr 23, 2015 at 20:15

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