Nico Nico Douga (ニコニコ動画) is a Japanese video-sharing service much like Website/YouTube. In fact, it started out as an online [=YouTube=] front-end before they were blocked from loading videos off [=YouTube=] servers. Now they host their own videos (for most language versions; for the English version they have somehow been allowed to do this again). Its trademark feature is the ability to add timed scrolling or subtitle-style captions to a playing video instead of offering a regular comments page like [=YouTube=]. This solves one problem (multiple pages required to see all comments on a [=YouTube=] video) while introducing a whole new one (see "Bullet Hell" below). Additionally, it has two features not originally seen on [=YouTube=] [[note]]Well, the live broadcast for [=YouTube=] eventually spawned.[[/note]] -- one is the "live broadcast", which is exactly what it sounds like, usually a concert or anime, and the other is the "International [=NicoNico=] Film Festival", where people compete to make a short film based upon a certain theme; there is a cash prize.

Despite the title, Nico Nico Douga isn't just limited to videos -- 2009 brought in sister sites [[http://seiga.nicovideo.jp Nico Nico Seiga]] and [[http://dic.nicovideo.jp Nico Nico Pedia]]. Seiga is the place where content creators post art, comics, and comment on other people's work {{Imageboard|s}} style. Later years allowed for official publishers to post chapters of their ongoing series, making for a handy site to catch up on lesser-known works. Pedia is the site's own [[TheWikiRule official wiki]], giving information on the characters, memes, and inside jokes that run rampant throughout. The popularity of these portions most likely contributed to the site being rebranded as "niconico" in 2012.

It is now available in [[http://www.nicovideo.jp Japanese]], [[http://es.nicovideo.jp Spanish]], [[http://de.nicovideo.jp German]], and [[http://tw.nicovideo.jp Chinese]] (the Chinese site is "tw" because that's where Niwango (the people who keep the site running) were told the most Chinese-language users were from, so don't start a political mess here). Registration is required; free membership (downgrades playback quality during peak hours) is available in all four languages, premium membership applications can only be purchased on the Japanese site but can then be carried over to any other language (credit card required, JCB or American Express from any country can be used while Visa and [=MasterCard=] issued outside Japan don't work, 500 yen or approx. US$6.20/month). There is no given timeline for carrying over the new player or site redesign over from Japanese to other languages (Taiwanese members now have a direct link to purchase premium membership).

In April 2011, a long-awaited, mostly functional English version went up. Also, an option to purchase premium memberships by [=PayPal=] was added, allowing international members without JCB cards or [=WebMoney=] vouchers to purchase it. There is also [[http://www.mmcafe.com/nico.html a redirector]] that allows viewing videos without having an account at the Japanese website.

On October 17, 2012, a full English version of the site was launched, rendering niconico.com obsolete.

!!This site is currently/was home to:
* AffectionateParody: NND is known for hosting a ''lot'' of these, skewering 2ch/an memes, anime, news, games...
* AllLowercaseLetters: Combined with CamelCase when the site rebranded to niconico.
* BlindIdiotTranslation: Version 1 of the Chinese site. It was little more than a script that Babelfished the Japanese site, leaving gaping holes in the translation and making the site hopelessly confusing. This is because it only had one meaning programmed in for each word and would translate part of words that weren't meant to be translated partially. When they released the Spanish and German translations they went and actually made a proper translation for the Chinese site.
** The Spanish translation is only about as good as Google Translate.
** The English version fares a bit better, but still suffers from a bit of poor translation, such as "authentification code".
* BulletHell: That's how people refer to a bunch of comments with the same phrase appearing in the same time. It's usually [[http://www.nicovideo.jp/watch/sm7137031 hilarious]], or downright [[http://www.nicovideo.jp/watch/sm1476140 awesome]].
** Becomes quite literal in some ''VideoGame/{{Touhou}}'' videos, especially with comments composed of Sakuya's knives. ─━╋ ─━╋ ─━╋ ─━╋ ─━╋ ─━╋
*** Such as in [[http://www.nicovideo.jp/watch/sm5748553 this]] [[GameMod automario]] rendition of "night of nights".
** There is also a tag for some of their videos: [[BulletHell Danmaku Song]]. [[http://dic.nicovideo.jp/a/%E5%BC%BE%E5%B9%95%E3%82%BD%E3%83%B3%E3%82%B0 The dictionary entry of that tag]] list several of those songs.
* CaramelldansenVid: The TropeMaker.
* CoverVersion: Tons of them, to the point where an entire tag was crafted for them. Many popular contemporary singers got their start as ''utaite'' on Nico Nico.
* FanConvention: Officially sanctioned festival "Nico Nico Choukaigi" serves as this for fans. It even comes with its own concert, "Nico Nico Cho Party", in the evening.
* LetsPlay: Players will record their playthroughs of some games and upload them with voiceover, much like how Western players do so, [[CaptainObvious except the voiceover is in Japanese]]. In some cases, these players may end up [[http://nicovideo.jp/search/fps playing through Western games]]. In rarer cases, ''crossovers'' may be used in the case of silent voiceover. Who knew ''VideoGame/{{Portal 2}}'' could be matched up with ''VideoGame/TheIdolMaster'', [[http://nicovideo.jp/watch/sm17943731 of all things]] (Or to be more accurate, Hibiki Ganaha as [[TheHero Chell]])?
* {{MST}}: The /a/ and /jp/ boards on Website/FourChan sometimes use the site to upload and mock videos from [=YouTube=]. Such videos include various {{fanime}} series ([[http://www.nicovideo.jp/mylist/10483090 example]]) and the infamous [[http://www.nicovideo.jp/watch/sm719083 report]] about the "[[NewMediaAreEvil hackers on steroids]]" group Anonymous.
** The Japanese users do something similar and there's even a tag for it: "Nico Nico International Cultural Exchange" or some such.
* StupidStatementDanceMix: Like its Western counterpart, Nico Nico is home to these. They even have common songs to back up the dance mixes, commonly referred to as "series".
* {{Troll}}: Since comments scroll across the video instead of being forced to the comments section which you can ignore, naturally, this can and often is [[{{GIFT}} used in the exact way you'd expect.]] Thankfully, it's ([[SurprisinglyGoodEnglish usually]]) not a problem if you don't know Japanese.
* TropeMaker: For ''-mita'' videos (''utattemita'',[[note]]"I tried to sing"[[/note]] ''odottemita'',[[note]]"I tried to dance"[[/note]], etc.), which eventually launched into their own media category (''utaite'' and ''odorite'' refer to those singers and dancers that started on Nico).