A judo match takes place between two players, on a mat, and is watched and scored by referees.
Within a judo match, the objective is to score an ippon, which is akin to a pin in wrestling or a knockout in boxing. When an ippon is scored, a match is over. There are three ways to attain an ippon:
- Throw the opponent over so that he lands hard on the back.
- Hold the opponent on the back for 25 seconds.
- Make the opponent submit by a strangle hold or an armlock.
There are hundreds of variations of throwing techniques. Some throws use mostly legs, some mostly arms, some a combination of arms, legs and torso. Some students throw their opponents over their own hips, shoulders or backs. They can also sweep the opponent's feet out from under him or drop down and throw the opponents over their own fallen body.
To pin an opponent, a student can press down from a facedown or side-down position (generally controlling the head and an arm or leg) so that the opponent's back or a shoulder is on the mat.
To obtain a submission, pressure can be applied directly on the elbow of a straight arm, or an arm bent at a right angle can be twisted in either direction (armlock). To strangle, or choke, pressure is applied to the sides of the opponent's neck (not the windpipe) by one or both forearms or by using the opponent's own collar. Strangle holds are only allowed on players 13-years-old or older. Arm locks can only be used if the player is at least 17-years-old.
Although strangles and armlocks may seem dangerous, the players are trained to know when they are in danger and will submit by tapping either the mat, or the opponent, twice, before any damage is done. The referees are extremely alert when one player attempts to apply a choke or an armlock. If the referee thinks the technique is about to cause serious injury, he can stop the match and declare a winner.
There is a long list of things not allowed. Mainly, players are expected to play fair and continuously attack. They are penalized for things like intentionally going out of bounds, refusing to attack (stalling), being too defensive, making rude comments or gestures and performing dangerous acts (like not giving the opponent a chance to submit). The rules are rarely broken except in the tactical areas, such as stepping out or stalling. Penalties in judo are severe; a repeat of any transgression results always in the next higher penalty, the lower one being removed.
Three referees officiate in a contest. Two sit at opposite corners and the third moves around the mat to observe the players. The center referee also controls the bout and signals the results. Each decision is agreed upon by at least two of the three referees.
Although an ippon is the objective, there are partial points scored. In each bout, however, it is the highest quality score that wins. A score is signaled by the referee's arm; the higher the arm signal, the higher the score. For example, an arm straight up signals an ippon.
How can you tell a technique's score?
Watch the center referee's hand signal and listen to the call. The higher the signaling arm, the higher the score. The scores, in order from highest to lowest quality are:
- Ippon : arm straight up.
- Waza-ari : arm out at shoulder level
- Yuko: arm 45 degrees out from the side
- Koka: arm against the side; hand in a sort of stop or greeting signal
Yuko is a lower grade of score, and only count as a tie-breaker; it is not cumulative with one another. Scoring is lexicographic; a waza-ari beats any number of yuko, but a waza-ari and a yuko beat a waza-ari with no yuko.
There used to be a fourth score called koka but it has been removed. When the koka was in use it was a lower score that yuko. Like yuko, koka is purely a tiebreaker and used only when competitors had the same amount of waza-ari and yuko. A yuko beats any number of koka.
A fifteen-second hold down scores yuko. If the person who secured the hold down already has a waza-ari, they only need to hold the hold down for twenty seconds to score ippon by way of two waza-ari (waza-ari-awasete-ippon). Throws further lacking the requirements of an ippon or a waza-ari might score a yuko. So-called "skillful takedowns" are also permitted (e.g. the flying arm-bar) but do not score.
If the scores are identical at the end of the match, the contest is resolved by the Golden Score rule. Golden Score is a sudden death situation where the clock is reset to match-time, and the first contestant to achieve any score wins. If there is no score during this period, then the winner is decided by Hantei, the majority opinion of the referee and the two corner judges.The contest area is a square eight meters long on each side. The outer meter (“danger area”) is red and is inside the playing area, but competitors can only remain in that area for a few seconds before attempting a throw or they will be penalized. There is a three-meter “safety area” in which a player can be thrown as long as the thrower remains inside the contest area.
 Sketch of a Mat |
There should be one or two scoreboards to show the state of play. Because in Judo it is always the highest quality score that wins, the scoreboard is laid out left to right to show the scores like 3-digit number.
| Waza-Ari | Yuko | KoKa | Medical | |
| Shido3 | Shido2 | Shido1 | ||
| BLUE | 0 | 3 | 1 | + + |
| WHITE | 1 | 0 | 0 | + |
| Shido3 | Shido2 | Shido1 |
Looked at in this way, the score is 100 to 31: White's single waza-ari beats the lesser quality of Blue's 3 yukos and 1 koka. Other features of the scoreboard are as follows:
- The Ippon score is not shown on the scoreboard because there can only be 1 Ippon and scoring it ends the bout.
- If two waza-ari's are scored by the same person it is considered the same as an Ippon and the match ends.
- On the above scoreboard, Blue has two medical timeouts; White has one. If blue needs another medical timeout, the match will end and white will be declared the winner.
- The boldface Shido2 on the White side indicates that one of Blue's Yukos was as a result of White's penalty. If White received another penalty, the Shido2 would be removed and the Shido3 would appear in boldface; on the Blue side, one Yuko would be removed and a Waza-Ari would be added. Penalties are explained in more detail in the next section
If an Ippon has not been scored by the end of the time limit, the player with the highest score wins; if tied, the clock score is cleared, the clock is reset to the same match time and the players enter “Golden Score” which means that the first score (or penalty) wins. Golden Score is a new rule in Judo for the 2004 Olympic Games. If the score is still tied after Golden Score, then the referee (1) and judges (2) decide who is the winner using a majority decision. They will each hold a blue flag in one hand and white flag in the other. On the referee's command of “HANTEI” (HAHN-TAY), each will indicate their vote by raising the flag having the same color of the uniform of the winner.
