What Counts as an Illegal Exposure
Five ways an exposure can be wrong, and the moment after which none of them can be corrected.
On this page
An exposure is the one thing you do in this game that everybody can see. All five of the mistakes below kill the hand, and each one usually stops being fixable the moment you discard — so the timing below is worth as much as the list.
Where a joker may sit, first
Three of the five ways to be wrong come straight off this one line. It usually pays to have it in front of you until it is automatic:
What a legal one looks like
The five
3. Exposing a single or a pair mid-hand
NEWS, a year, 336699 — tightly printed but separate tiles. They may only be completed by the tile that declares mahjong, so putting them on the table before then is an illegal exposure.
4. Exposing anything on a concealed line
A hand marked C stays in your rack. It may hold jokers, it may redeem jokers, and it may claim a discard to win — but the moment you expose a grouping on a C line, the hand is dead.
5. Putting tiles down for a claim you do not win
The one nobody warns you about. If you lay tiles out and somebody else turns out to have the better claim, you have exposed tiles without successfully claiming anything — a violation in its own right, and it kills your hand. Wait until the tile is yours.
Call. Wait for competing claims to settle. Then lay the tiles down. Most tables compress those into one motion and get away with it, because most discards are uncontested.
The window in which it is still fixable
Here is the part worth knowing, because it is the difference between a mistake and a dead hand.
An exposure stays editable until you discard on the turn you made it. Before that you may add to it, correct it, or take the whole thing back. After you discard it is frozen for the rest of the hand — a wrong exposure can no longer be fixed, only challenged.
Starting a joker redemption locks your own exposures for the rest of the game, even if you have not discarded yet. So if something about your exposure is bothering you, sort it out before you reach for a joker.
Some of these cannot be argued
Most dead-hand challenges are a two-step exchange: somebody challenges, and you either acknowledge it and stop playing, or deny it and carry on without saying what you are making. Whoever turns out to be wrong pays the other 50.
A plainly illegal exposure is not one of those. Like a wrong tile count, it makes the hand dead immediately — there is nothing to dispute, because the evidence is face up on the table in front of everybody.
Tiles you were in the middle of exposing when challenged go back into your rack. Exposures you had already completed stay visible, and their jokers generally remain available for redemption — with exceptions where the exposure itself reveals that the hand could never have won. Exactly where that line falls depends on which source you read, so expect your table to decide it rather than look it up.
When you have read it all: the rules workbook, 105 questions with an answer key that cites the rule behind every answer, $19.
Where this comes from
That a joker is never legal in a single or a pair, the singles-and-pairs claiming restriction and the concealed-hand rule are confirmed independently by the American Mah-Jongg Association's rulebook, Tom Sloper's rules FAQ and I Love Mahj. The joker ceiling on a quint — four during play, five when declaring mahjong — is the AMJA's. That exposing without a successful claim is itself a violation we found in the AMJA's rulebook only; the other sources do not address it either way.
The edit window and the redemption lock are confirmed by Sloper, which cites the League's own rulebook, and by I Love Mahj. That an illegal exposure is not disputable is the AMJA's. What survives a dead hand is where the sources genuinely differ, and we have said so rather than pick a side.