A cap (キャップ, kyappu), often called a capcode, is a unique identifier used to prevent impersonation on anonymous bulletin boards, typically handed out to the website's staff or special users. The feature comes from 2channel in late 1999, long before the creation of the trip in 2002.

It was initially called the “impersonation prevention feature” (成りすまし防止機能, narisumashi bōshi kinō), but 2channel founder Hiroyuki saw that “bōshi” (機能, lit. “feature”) was a homophone with “bōshi” (帽子, lit. “hat”), so he ended up dubbing it a “cap” (キャップ, kyappu).

The feature later became known as a “capcode” since the early English translators for World2ch decided to compare the “cap” and “trip” to a “passcode” when they attempted to translate their FAQ guide¹⁾ in 2003.²⁾ Admittedly, it probably would've been a headache if the Japanese terms were translated literally, being forced to explain the etymology when the wordplay isn't really that important to go over.

For starters, the traditional method of using a capcode is to insert a special string in the email field of a post form, causing the name to change accordingly upon submitting. On 2channel and Shitaraba, this results in the designated name with a star (★) that will turn into an empty star (☆) when people attempt to impersonate you, but some boards and scripts use different methods.

With the introduction of tripcodes, 2channel has been very selective with capcodes, only gifting them out to people within management (e.g. administrators, developers, moderators, emeriti) and users who apply to become a reporter on the plus boards. In late 2014, a “cap stopper” was added, allowing users to terminate a leaked capcode by inputting “#DEL:” before the cap's password in the email field.³⁾

Historically, “fusianasan” was the initial capcode for 2channel founder Hiroyuki, but it eventually leaked on September 23, 1999. After reverting the damage, using the capcode would cause the user's “remote host name” to be revealed, which turned this into a tool to troll newcomers or expose users posting inappropriate content. Recently, it's rumored that 5channel removed it in 2017.

Considering that Shitaraba (formerly JBBS) is a website that allows people to manage their own boards, the feature is offered but named “handle password” (ハンドルパスワード, handoru pasuwādo) instead. These capcodes can be registered in the management panel with custom colors, but note that capcodes must start off with a number sign (#) when the designated user enters them into the email field.⁴⁾

The capcodes on 4chan are typically restricted to logged-in registered users who input “pubies” in the email field, according to a 2010 leak,⁵⁾ thought it's possible that this might've changed. This will result in a colored name and, if the user is a Team 4chan member, variant of the 4chan icon. The tooltip states the obvious if the user is apart of Team 4chan, but shows a member's ID on 4chan's /j/ board instead.

• Anonymous ## Founder - This capcode is supposed to be used by Christopher Poole (moot) but it hasn't been used yet. In his final 4chan Q&A, he called it the “Admin Emeritus” capcode.
• Anonymous ## Admin - This capcode is used by the administrator, “hiroyuki”, and those who manage to hack into the 4chan administration panel. In the past, this was primarily used by “moot”.
• Anonymous ## Manager - This capcode might've been restricted to /j/,⁶⁾ but was first spotted outside of it in /qa/ around 2016. It seems like they can fire moderators and rogue janitors.
• Anonymous ## Mod - This capcode is used by mods that perform site maintenance (e.g. delete/ban on all boards, sticky/close/autosage threads, etc.). They should not be confused with janitors.
• Anonymous ## Developer - This capcode is given to developers who are involved with developing the proprietary software, Yotsuba, and were first spotten on August 8, 2012 in /q/.
  • Anonymous ## BlOgGeR - In the leaked source code, this capcode was for Randall Munroe of xkcd, who would have to input “munroexkcd” in the email field.
• Anonymous ## Verified - This capcode is granted to notable people unaffiliated with “Team 4chan” and it has been actively used by “Tattun” in recent years.
  • Anonymous ## Verified - This capcode might be an early variant of the “Verified” capcode, used by Andrew W.K. and Deadmau5 in 2011.

For websites that use Tinyboard, Vichan, Lainchan, and its derivatives, capcodes are similar to tripcodes as logged-in users will use the name field, inputting “## Admin” for ## Admin or “## Mod” for ## Mod. Without proper permissions, it'll spit out a secure tripcode. Also, do note that administrators aren't bound to ## Admin as it allows for custom capcodes, such as ## God or whatever.

• As mentioned, the homophone doesn't translate well to non-Japanese langauges.
  • In the Chinese language, it becomes “jīnéng” (机能, lit. “function”) and “màozi” (帽子, lit. “hat”).
  • In the Korean language, it becomes “gineung” (기능, lit. “function”) and “moja” (모자, lit. “hat”).

• ★ on 2channel's Wiki
• Cap (Electronic Bulletin Board) on Japanese Wikipedia
• Cap (Electronic Bulletin Board) on Niconico Encyclopedia