Forehead Protector

A is a headband composed of a metal plate and a band of cloth. Forehead protectors are worn by most shinobi and are engraved with the symbol of their hidden village. Forehead protectors have been worn since at least the time of Asura Ōtsutsuki, though there was no engraving then.

Meaning
Forehead protectors are usually worn as a sign of pride and fealty for one's village. Ninja consider it an honourable, important part of their tradition, and make a point of wearing it at all times, especially when sparring with a comrade from the same village. Although not wearing a forehead protector is frequently viewed as disrespectful to one's village and peers, a ninja who does not wear one may still be loyal to their village. Similarly, to have one's protector removed is to denote one's unworthiness to the name "ninja", as Naruto did to Boruto for cheating during the Chūnin Exams.

Some missing-nin, such as Zabuza Momochi, continue wearing their forehead protector even after they've left their village. Akatsuki members who retain their forehead protectors carve a long, horizontal scratch across the symbol, to show they have rescinded their allegiances and rejected their villages. Villagers of Amegakure aligned with Pain bear the same scratches across their forehead protectors, but remain loyal to the village; it symbolises their victory during the civil war against Hanzō.

In preparation for the Fourth Shinobi World War, Mifune designs a new forehead protector to be worn by members of the Allied Shinobi Forces. Engraved with the kanji for, it symbolises that, whereas once each ninja fought for their villages separately, they now stand united under one banner for the same cause. The members of the Alliance wear this in place of their original forehead protector.

Placement
Despite being called a "forehead protector", it is not necessary for a ninja to wear it on their forehead or even on their head at all.
 * Sakura Haruno wears hers as a hair-band.
 * Genma Shiranui wears his like a bandanna with the village symbol facing backward.
 * Kankurō wears his on his hood.
 * Kakashi Hatake wears his as a makeshift eye-patch.
 * Hinata Hyūga wears hers around her neck.
 * Shikamaru Nara wears his on his upper left arm.
 * Chōjūrō uses his like a badge on his chest.
 * Yagura Karatachi uses an undershirt in which his protector is in the middle.
 * Gaara wraps his on his sand gourd.
 * Might Guy and Rock Lee wear theirs as a belt.
 * Ino Yamanaka ties hers around her midsection in Part I.
 * Konan's is not ordinarily visible; she wears hers underneath her cloak on her right hip.
 * Sasuke Uchiha keeps his forehead protector on him at his waist as a symbol of his friendship with Naruto.

Colour

 * Navy Blue: The most common colour of forehead protectors. Many ninja keep this colour for the entirety of their ninja career.
 * Black: The second most common colour of forehead protectors. Some, such as Naruto Uzumaki, even switch from blue to black after the timeskip.
 * Crimson: Common among ninja of Iwagakure. Also used by Rock Lee and Might Guy and, after the timeskip, Sakura Haruno and Chōji Akimichi.
 * White: Though rarely seen, several Kumogakure ninja use it, as do the Four Celestial Symbols Men.
 * Purple: Has been used by those loyal to Otogakure and Hoshigakure. Inoichi Yamanaka and the Gold and Silver Brothers also use purple.
 * Brown: Seen briefly in the ninth OVA, worn by a Kumokagure genin.
 * Dark Green: Has been used by genin of Kusagakure in the anime: Team Kazami.

Design
There have been some cases where the design of the metal plate or cloth has been modified in some way, beyond mere cloth colour.

Trivia

 * On the cover for chapter 567, each jinchūriki is shown with a white forehead protector with the kanji for the number of tails of their respective tailed beasts.
 * Masashi Kishimoto, in an interview, noted that he created forehead protectors because he found it too cumbersome to draw Naruto's goggles every week.
 * In episode 27 of Naruto SD: Rock Lee no Seishun Full-Power Ninden, Chōza is seen wearing a forehead protector with the kanji "shinobi", similar to the ones worn by the shinobi of the Allied Shinobi Forces.
 * Upon imagining his life if he had returned to Konoha after Rin Nohara's death, Obito depicted himself wearing a modified forehead with covers that stretch down his left eye to conceal his empty eye socket.