This article describes the rules of judo. The main sections of the article describe the rules that apply to any situation in which judo is practiced, and those rules which apply only in judo competitions.
In practice and competition
Safety
Intentionally injuring an opponent is not permitted. Punching, kicking, and other strikes are not allowed. Touching the opponent's face is not allowed. Attacking joints other than the elbow is not allowed. Long hair touch for boys are not permitted. The technique known as kawazu gake is not permitted. The technique known as kani basami is not permitted. Wearing any hard or metallic object during competition is not permitted. The penalty for violating this rule is hansoku make (see Penalties, below). This includes wedding rings, earrings, hard-plastic protective gear, hair-ties with metal parts, wristwatches, and even press-studs on underpants. For female judokas, hair with longer length must be tied either in a pony tail or a hair bun (neat or messy). A plain white T-shirt must be worn.
Etiquette
Contestants must bow before stepping onto the mat. Contestants must bow to each other before and after practice or competition. Inappropriate behaviour, such as foul language and bodily gestures, is not tolerated.
In competition only
Stalling is not permitted. Using a defensive posture is not permitted. It is required to bow to the competition area. False attacks are not permitted. They are considered attempts to circumvent the prohibition against noncombativity. Disregarding the orders of the judge is prohibited.
Scoring
The scoring rules in use starting in 2017 are as follows: Awarding of ippon (一本) 'One full point'. Award of ippon decides the winner and ends the match. Ippon is awarded for a successful throw performed with control and power, or for a pin lasting 20 seconds. Submission by strangulation or application of an arm lock at the elbow joint also results in ippon. Awarding of waza-ari (技あり). 'One half point'. Awarded for a successful throw lacking one of the above elements, or for a pin lasting 10 to 19 seconds. With the exception of 2017, two waza-ari also wins the match (announced as “waza-ari awasete ippon,” or “waza-ari together [with a previously-earned waza-ari] makes ippon”).
The following rules are no longer in use:
Awarding of yuko (有効). One score of waza-ari was considered greater than any number of yuko scores. From 2008 to 2016, yuko was the smallest score that can be awarded. Yuko was removed from IJF competition in 2017. Awarding of koka (効果). Was introduced in 1975 and removed from IJF competition at the end of 2008. Any number of koka scores does not add up to a yuko score.
Penalties
Two types of penalties may be awarded. A shido (指導; literally "guidance" or "instruction") is awarded for minor rule infringements. A shido can also be awarded for a prolonged period of non-aggression. Recent rule changes allow for the first shidos to result in only warnings. If there is a tie, the number of shidos for each player are not used to determine the winner. After three shidos are given, the victory is given to the opponent. This is an indirect hansoku-make, and does not result in expulsion from the tournament. The penalty of hansoku make (反則負け; literally "foul-play loss") is awarded for major rule infringements, or for accumulating three shidos. If hansoku make is awarded for a major rule infringement, it results not just in loss of the match, but in expulsion from the tournament. Note: Prior to 2017, the 4th shido was hansoku make.
Competition area
The competition area must be padded with tatami. The minimum allowable size is . The match takes place in an to zone within this larger area. The surrounding space acts as a safety zone. When two competition areas are side by side, there must be at least a 3-meter (10-foot) safety zone between them.
Grips
Rules related to grips are primarily motivated by the desire to avoid stalling, to avoid providing undue advantage, or to reduce the chance of injury.