Kōhaku Uta Gassen

The songs and performers are examined by a selection committee put together by NHK. The basis for selection are record sales and adaptability to the edition's theme.

At the same time, a demographic survey is conducted regarding the most popular singers for each and what kind of music people want to hear. This and the song selection explain the amalgamation of the musical genres and its artists.

There are, however, exceptions to the process. Momoe Yamaguchi chose to sing her favorite song "Hito Natsu no Keiken" (ひと夏の経験) with its suggestive lyrics during the 25th edition, despite NHK's pick of a different song.

When the show was first broadcast on radio in 1951, each team had a few performers, all of whom would perform within an hour. Since 1989, the program goes on for at least four hours as both teams, each having at least 25 performers, perform their songs.

At the end of the show, the audience and a panel of judges—notable celebrities who may or may not have a connection to the music industry—vote to select the winning team. In the past, the audience vote has been composed of a head count of the venue audience members, who could vote for either team (NHK Hall, which has been the venue for most Kōhaku editions since 1971, can seat 3,000 people). This counted as one vote.

As of the 54th (2003) and 55th editions (2004), viewers who watch the program through ISDB-S on NHK BS Hi-vision could vote by having their own head count in their respective households. Although it was still sketchy to determine in the 55th, the audience vote was counted as two votes: one for the venue audience and one for ISDB-S viewers.

The audience vote(s) are added to those of the judges who each have to vote for one team. The team with the most votes wins.

The above process was done differently for the 56th edition (2005). Instead, the NHK Hall head count, the vote count from cellphone users and the vote count from ISDB-S viewers each counted as one vote. As stated above, the team that got at least two votes won.

In the 57th edition (2006), aside from cellphone and ISDB-S viewers and the NHK Hall audience, 1seg users voted. Its format had been reverted to the ball voting system—from the audience head count and the judges' votes.

From the 58th edition (2007) to the 63rd edition (2012) and again in the 65th (2014), 66th (2015), and 68th (2017) through 70th editions (2019), the winner was determined through an overall head count, all from cellphone, ISDB-S viewers, 1seg users, and the NHK Hall Audience (including guests). Voting reverted temporarily to judges plus audience-unit votes in the 64th edition (2013) and 67th (2016) except that viewing audience votes (from internet, cellphone, digital TV, and 1seg voting) during halftime and end of show would each count as one vote and the NHK Hall head count as another single vote. The 71st edition (2020) featured off-venue voting only as there was no live audience in attendance due to concerns that arose from the COVID-19 pandemic in Japan. The 71st edition also saw performances emanating from multiple venues within NHK's studio premises with NHK Hall still the main staging area.

Aside from the performances, there are special performances where certain performers do their act together, the so-called "Ring Show" where performers from both teams take part in a "singing exercise," as well as performances from non-competing artists both in Japan and abroad. At the end of the show, all the performers sing "Hotaru no Hikari" (蛍の光) together. The song is based on the Scottish "Auld Lang Syne" that is commonly sung at New Year parties in the west. In addition, the 50th edition of the show included a "Countdown Special" to welcome the year 2000.

A special celebrating the 100 years of broadcasting is scheduled to air on March 25, 2025. More than 10,000 submissions were received from the public, who shared their favorite and most memorable moments from all broadcasts. Teruyoshi Uchimura, Yo Oizumi, Mone Kamishiraishi, and announcer Maho Kuwako serve as hosts of the special program "100 Years of Broadcasting Project: Everyone's Best Kohaku", airing on March 25, recorded at NHK Hall, Kohaku's venue since 1973. The cast includes Kiyoshi Hikawa, Hiromi Go, Akira Fuse, AI, Nogizaka46, and Golden Bomber. Kazunari Ninomiya is scheduled for a guest appearance. Performers talk about their "Kohaku" memories and sing songs that meet this theme.^[3] Previous to the program, a special Songs [ja] will air on March 13, with guests, including Lady Gaga, commenting about their experiences on Kohaku.^[4][5][6]

Kōhaku was once the most-watched show on Japanese television of the year. One major factor was that New Year's Eve in Japan is a holiday traditionally spent at home (see Ōmisoka). Over the years, the annual event's popularity has declined from an all-time high of an 81.4 rating in 1963 to a low of 30.6 in the Kantō region for the first part of the 2006 event.^[8] The 2021 Kōhaku program set a record low for the second portion of the show with a 34.3 viewership rating in the Kantō region.^[9] Despite the drop, Kōhaku is consistently the top-rated musical event each year.^[10]

Outside Japan, Taiwan also hosts a similar Kōhaku competition, Super Star (超級巨星紅白藝能大賞), which broadcasts on the eve of Chinese New Year. Similar to Kōhaku, the special is held at a live venue, Taipei Arena. Unlike Kōhaku, Super Star does not have gender-affiliated teams and the special is pre-recorded weeks before airing instead of being a live broadcast. The first special premiered on February 13, 2010, the eve of the 2010's Chinese New Year.^[11] The most recent special was set to be broadcast on February 9, 2024.