The blue and white judogi exist to tell the two players apart. At IJF events, the first judoka called wears white and the second wears blue. The rule dates from the late 1990s and traditionalists still argue about it. Beyond color, a whole set of rules covers the judogi: jacket and sleeve dimensions, belt and back number. A check takes place before each match.
At many club, local and regional events around the world, both players still wear white, with a red or white belt added on top to distinguish them. Blue becomes standard as the level rises.
Why a blue judogi and a white judogi?
The idea came from Anton Geesink, the Dutch world and Olympic champion, who proposed it to the IJF in the mid-1980s. His argument was practical: two white judogi blur together for referees, spectators and television. It took around a decade and several rejected votes before adoption.
Opposition came mainly from Japan, attached to white as the symbol of judo. The Kodokan still uses the white judogi, and many dojos worldwide use nothing else. For the cultural background, see our page on the Kodokan.
Looking back, we think Geesink was right for competition. Video refereeing would be far harder without two colors.
Who wears blue?
The IJF rule is mechanical. The judoka called first wears white, the second wears blue. Color has nothing to do with ranking or grade. The same player can switch from white to blue between two matches on the same day.
That creates a constraint: competitors must bring both judogi. At its events, the IJF requires judogi approved by the IJF, and the shade of blue is regulated too. National events set their own requirements, so read the invitation.
In all-white events, the colored belt worn on top does the same job. The event rules say who wears which.
The judogi control
Before each match at major events, an official checks the judogi. They use a gauge called the sokuteiki to measure it. Among the points checked:
- sleeve length, which must reach close to the wrist when the arm is stretched forward;
- sleeve width, with enough room between fabric and arm along the whole length;
- jacket length, which must cover the buttocks;
- the overlap of the lapels and their thickness;
- the length of the trousers and the belt.
These rules exist because a short or tight sleeve stops the opponent from gripping. For years some competitors wore fitted jackets to frustrate the other player's kumikata (gripping). The control ended that.
A judogi that fails the check is refused. On the international circuit, the judoka has to change before being allowed to fight. The exact measurements are in the IJF judogi rules, which remain the only reliable reference.
Back numbers and identification
At international events, each judogi carries a back number sewn on the back, with the athlete's name and country code. Its size and position are regulated. Advertising marks are also allowed within strict limits.
Back numbers are not required at every level. National championships have their own rules, published by the federation.
Other dress rules
A few points that earn remarks or penalties in competition:
The belt. It must be tied tightly with a square knot, the ends a reasonable length. A belt that comes undone on every exchange wastes time and can bring a warning. The right knot is shown in our page on how to tie a judo belt.
Long hair is tied back with a soft band. Nothing hard or metal.
Women wear a white T-shirt under the jacket. Short nails and no jewellery for everyone.
The judogi must be clean and dry, with no smell. It sounds obvious, yet a referee can refuse a dirty one.
Taking too long to fix your judogi between matte and hajime brings a warning first. Since the 2026 rule adjustment, it then becomes a shido. The details are in our article on shido penalties.
Choosing a competition judogi
For training, any comfortable judogi will do. For competition, choose the size with the control in mind: a judogi that shrinks after washing can be refused. Our judo gi size chart helps you get it right. The rest of the rulebook is in our guide to judo rules.
Our advice: wash your competition judogi cold and never put it in the dryer. Cotton that shrinks two centimeters at the sleeves can be enough to fail the check, and it never happens on the day you expect. More care tips are in our guide on how to wash a judo gi.