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==Variants==

=== Freestyle gomoku ===
Freestyle gomoku has no restrictions on either player and allows a player to win by creating a line of five or more stones, with each player alternating turns placing one stone at a time.

==== Swap after 1st move ====
The rule of "swap after 1st move" is a variant of the freestyle gomoku rule, and is mostly played in China.  The game can be played on a 19×19 or 15×15 board. As per the rule, once the first player places a black stone on the board, the second player has the right to swap colors. The rest of the game proceeds as freestyle gomoku. This rule is set to balance the advantage of black in a simple way.<ref>{{Cite web |title=Swap after 1st move rule |url=http://www.wuzi8.com/Article/HTML/3764.html |archive-url=https://web.archive.org/web/20211208090454/http://www.wuzi8.com/Article/HTML/3764.html |archive-date=2021-12-08 |access-date=2023-04-28 |website=www.wuzi8.com |language=zh}}</ref>

=== Renju ===
Black (the player who makes the first move) has long been known to have an advantage, even before [[L. Victor Allis]] proved that black can force a win (see below). [[Renju]] attempts to mitigate this imbalance with extra rules that aim to reduce black's first player advantage.

It is played on a 15×15 board, with the rules of three and three, four and four, and overlines applied to Black only.<ref name=":6" />
* The rule of three and three bans a move that simultaneously forms two open rows of three stones (rows not blocked by an opponent's stone at either end).
* The rule of four and four bans a move that simultaneously forms two rows of four stones (open or not).
*Overlines prevent a player from winning if they form a line of 6 or more stones.<ref name=":6" /><ref>{{Cite web |title=The Renju International Federation portal - RenjuNet |url=https://www.renju.net/advanced/ |access-date=2021-07-22 |website= |archive-url=https://web.archive.org/web/20210711201520/https://www.renju.net/study/advanced.php |archive-date=11 July 2021 |url-status=dead}}</ref>
Renju also makes use of various tournament opening rules, such as [[Soosõrv opening rule|Soosõrv-8]], the current international standard.<ref>{{Cite web|title=The Renju International Federation portal - RenjuNet|url=http://renju.net/ga2015/|url-status=live|archive-url=https://archive.today/20210722180937/http://renju.net/organizations/ga2015.php|archive-date=2021-07-22|access-date=2021-07-22|website=renju.net}}</ref>

=== Caro ===
In Caro, (also called gomoku+, popular among Vietnamese), the winner must have an overline or an unbroken row of five stones that is not blocked at either end (overlines are immune to this rule). This makes the game more balanced and provides more power for White to defend.<ref>{{Cite web|title=Caro (aka Gomoku)|url=https://learnplaywin.net/caro/|url-status=live|archive-url=https://web.archive.org/web/20210722180806/https://learnplaywin.net/caro/|archive-date=2021-07-22|access-date=2021-07-22|website=LearnPlayWin|language=en-US}}</ref>

=== Omok ===
Omok is similar to Freestyle gomoku; however, it is played on a 19×19 board and includes the rule of ''three and three.''<ref name=":8">{{Cite web|date=2016-10-06|title=Omok: A Korean Game of Five Stones.|url=https://kpopjacketlady.com/2016/10/06/omok-a-korean-game-of-five-stones/|url-status=live|archive-url=https://web.archive.org/web/20210722180238/https://kpopjacketlady.com/2016/10/06/omok-a-korean-game-of-five-stones/|archive-date=2021-07-22|access-date=2021-07-22|website=KPOP Jacket Lady|language=en}}</ref><ref name=":7">Sungjin, Nam. "Omok." ''Encyclopedia of Korean Folk Culture'', National Folk Museum of Korea, https://web.archive.org/web/20210722180119/https://folkency.nfm.go.kr/en/topic/detail/1587 . Accessed 22 July 2021.</ref>

=== Ninuki-renju ===
Also called Wu, Ninuki Renju is a variant which adds capturing to the game; A pair of stones of the same color may be captured by the opponent by means of custodial capture (sandwiching a line of two stones lengthwise). The winner is the player either to make a perfect five in a row, or to capture five pairs of the opponent's stones. It uses a 15x15 board and the rules of three and three and overlines. It also allows the game to continue after a player has formed a row of five stones if their opponent can capture a pair across the line.<ref>{{Cite web|title=Rules of Pente, Keryo-Pente and Ninuki|url=https://renju.nu/pente-rules/|url-status=live|archive-url=https://web.archive.org/web/20210722180425/https://renju.nu/pente-rules/|archive-date=2021-07-22|access-date=2021-07-22|website=Renju|language=en-US}}</ref>

=== Pente ===
[[Pente]] is related to Ninuki-Renju, and has the same custodial capture method, but is most often played on a 19x19 board and does not use the rules of three and three, four and four, or overlines.<ref>{{Cite web|title=Pente|url=https://www.mindsports.nl/index.php/the-pit/546-pente|url-status=live|archive-url=https://web.archive.org/web/20210701212828/https://www.mindsports.nl/index.php/the-pit/546-pente|archive-date=2021-07-01|access-date=2021-07-22|website=www.mindsports.nl}}</ref>[[File:Pro Gomoku.jpg|thumb|'''Pro''' Opening Rule: Black places first stone in the center of board. White can place anywhere, but places to the South-East. Black places their second stone three spaces away.]]

=== Tournament opening rules ===
Tournament rules are used in professional play to balance the game and mitigate the first player advantage. The tournament rule used for the gomoku world championships since 2009 is the Swap2 opening rule. For all of the following professional rules, an overline of six or more stones in a row does not count as a win.<ref name=":3" />
[[File:Swap Rule Gomoku.jpg|left|thumb|'''Swap''' Opening Rule: Tentative Black places two black stones and one white stone anywhere on the board. Tentative white chooses which color to play as.]]

==== Pro ====
The first player's first stone must be placed in the center of the board. The second player's first stone may be placed anywhere on the board. The first player's second stone must be placed at least three intersections away from the first stone (two empty intersections in between the two stones).<ref name=":4">{{Cite web|title=Opening rules {{!}} GomokuWorld.com|url=http://gomokuworld.com/gomoku/2|url-status=live|archive-url=https://web.archive.org/web/20210722164403/http://gomokuworld.com/gomoku/2|archive-date=2021-07-22|access-date=2021-07-07|website=gomokuworld.com}}</ref>

==== Long Pro ====
The first player's first stone must be placed in the center of the board. The second player's first stone may be placed anywhere on the board. The first player's second stone must be placed at least four intersections away from the first stone (three empty intersections in between the two stones).<ref name=":4" /><ref>{{cite web | access-date=2021-07-28 | url=https://www.renju.net/rule/7/ | title=Gomoku – pro rule | website=www.renju.net}}</ref>
[[File:Swap2 Gomoku.jpg|thumb|'''Swap2''' Opening Rule: Tentative Black places two black stones and one white stone anywhere on the board. Tentative White responds by picking option number three and placing two more stones, one of each color, on the board and passes the choice of which color to play as to tentative Black.]]

==== Swap ====
The tentative first player places three stones (two black, and one white) anywhere on the board. The tentative second player then chooses which color to play as. Play proceeds from there as normal with white playing their second stone.<ref name=":4" />

==== Swap2 ====
The tentative first player places three stones on the board, two black and one white. The tentative second player then has three options:

# They can choose to play as white and place a second white stone
# They can swap their color and choose to play as black
# Or they can place two more stones, one black and one white, and pass the choice of which color to play back to the tentative first player.

Because the tentative first player does not know where the tentative second player will place the additional stones if they take option 3, the swap2 opening protocol limits excessive studying of a line by only one of the players.<ref name=":9" /><ref name=":4" />