If the scores are equal when all the object balls have been potted, the black is used as a tiebreaker. In this situation, called a "re-spotted black", the black ball is returned to its designated spot and the cue ball is played in-hand, meaning that it may be placed anywhere on or within the lines of the "D" to start the tiebreak. The referee then tosses a coin and the winner of the toss decides who goes first. The game continues until one of the players either pots the black ball to win the frame, or commits a foul (losing the frame).
Professional and competitive amateur matches are officiated by a referee, who is charged with ensuring the proper conduct of players and making decisions "in the interests of fair play". The responsibilities of the referee include: announcing the points scored during a break; announcing the penalty points awarded after a foul has been committed; replacing colour balls onto their designated spots after being potted; and cleaning the cue ball or any object ball upon request by the striker. Another duty of the referee is to recognise and declare a stalemate when neither player is able to make any progress in the frame. If both players agree, the balls are returned to their starting positions and the frame is restarted (known as a "re-rack"), the same player taking the break-off shot as before. Professional players usually play the game in a sporting manner, declaring fouls they have committed which the referee has not noticed, acknowledging good shots from their opponent, and holding up a hand to apologise for fortunate shots, known as "flukes".
Points in snooker are gained from potting the object balls in the correct sequence. The total number of consecutive points (excluding fouls) that a player amasses during one visit to the table is known as a "break". A player could achieve a break of 15, for example, by first potting a red followed by a black, then another red followed by a pink, before failing to pot the next red. A maximum break in snooker is achieved by potting all reds with blacks, then potting all six colours, yielding 147 points; this is often known as a "147" or a "maximum". As of 20 January 2021[update], there are 166 confirmed instances of players scoring a maximum break in professional competition.
Penalty points are awarded to a player when a foul is committed by the opponent. A foul can occur for various reasons, most commonly for sending the cue ball into a pocket, or for failing to hit the correct object ball (e.g. hitting a colour first when attempting to contact a red). The latter is a common foul committed when a player fails to escape from a "snooker", where the previous player has left the cue ball positioned such that no legal ball can be struck directly in a straight line without being wholly or partially obstructed by an illegal ball. Fouls incur a minimum of four penalty points unless a higher-value object ball is involved in the foul, up to a maximum of seven penalty points where the black ball is concerned. When a foul is committed, the offender's turn ends and the referee announces the penalty. All points scored in the break before the foul was committed are awarded to the striker, but no points are scored for any ball pocketed during the foul shot.
If dissatisfied with the position left after a foul, the next player may request that the opponent who committed the foul should be made to play again from where the balls have come to rest. If the foul has left no valid shot available for the next player, the referee may call a free ball, allowing the player to "nominate" any object ball in place of the shot they might normally have played. Doing so with all 15 red balls still in play can potentially result in a break exceeding 147, with the highest possible being a 155 break, achieved by nominating the free ball as an extra red, then potting the black as the additional colour after potting the free-ball red, followed by the 15 reds with blacks, and finally the colours. Jamie Cope is recorded as being the first player to post a verified 155 break, achieved in a practice frame in 2005, with other players such as Alex Higgins claiming to have made a similar break.
One game of snooker, beginning with the balls in their starting positions and ending when the last ball is potted, is called a "frame". A snooker match generally consists of a predetermined number of frames and the player who wins the most frames wins the match. Most professional matches require a player to win five frames, and are called "best of nine" in reference to the maximum possible number of frames. Tournament finals are usually best of 17 or best of 19, but some tournaments, such as the World Championship uses longer matches – ranging from best of 19 in the qualifiers and the first round up to best of 35 for the final (first to 18), and is played over four sessions of play held over two days.
Professional snooker players compete on the World Snooker Tour, which is a circuit of ranking tournaments and invitational events held throughout the snooker season. All competitions are open to professional players who have qualified for the tour, and selected amateur players, but most events include a separate qualification stage. Players can qualify for the tour either by virtue of their position in the world rankings from prior seasons, by winning continental championships, or through the Challenge Tour or Q School events. Players on the World Snooker Tour generally gain a two-year "tour card" for participation in the events. Reflecting the game's aristocratic origins, the majority of tournaments on the professional circuit require players to wear waistcoats and bow ties. The necessity for this rule has been questioned, and players such as Stephen Maguire have been granted medical exemptions from wearing a bow tie.
The global governing body for professional snooker is the World Professional Billiards and Snooker Association (WPBSA), founded in 1968 as the Professional Billiard Players' Association. The WPBSA owns and publishes the official rules of snooker, and has overall responsibility for policy-making in the professional sport of snooker. World Snooker (rebranded the "World Snooker Tour" in 2020) is the wholly owned commercial subsidiary of WPBSA responsible for the professional tour.
Every player on the World Snooker Tour is assigned a position on the WPBSA's official world ranking list, which is used to determine the seedings and the level of qualification each player requires for the tournaments on the professional circuit. The current world rankings are determined using a two-year rolling points system, where ranking points are allocated to the players according to the prize money earned at designated ranking tournaments. This "rolling" list is maintained and updated throughout the season, with points from tournaments played in the current season replacing points earned from the corresponding tournaments of two seasons ago. Additionally, "one-year" and "two-year" ranking lists are compiled at the end of every season, after the World Championship; these year-end lists are used for pre-qualification at certain tournaments and for tour-card guarantees.
The top 16 players in the world ranking list, generally regarded as the "elite" of the professional snooker circuit, are not required to pre-qualify for some of the tournaments, such as the Shanghai Masters, the Masters and the World Snooker Championship. Certain other events, such as those in the Cazoo Cup series, use the one-year ranking list to qualify; these use the results of the current season to denote participants. As of the 2020–21 season, there are 128 places available on the World Snooker Tour, with players either in the top 64 on the official ranking list, or finishing as one of the top eight prize money earners during the most recent season, guaranteed a tour place for the next season, this being assessed after the World Championship.
The oldest current professional snooker tournament is the World Snooker Championship, which has taken place annually since 1927 (except during World War II and between 1958 and 1963). The tournament has been held at the Crucible Theatre in Sheffield, England, since 1977, and was sponsored by Embassy from 1976 to 2005. Since the ban on advertising tobacco products, the championship has been sponsored by various betting companies. It is televised extensively in the UK by the BBC, and receives significant coverage in Europe on the Eurosport network, and in East Asia on CCTV-5. The first official snooker tournament was the 1908 American Tournament [it], held between 1907 and 1908 and won by Charles Dawson when the sport was used as an extra feature to billiard matches.
The World Championship is the most highly valued prize in professional snooker in terms of financial reward (£500,000 for the winner since 2019), ranking points, and prestige. The World Championship is part of the Triple Crown Series, along with the UK Championship and the non-ranking Masters tournament. The Triple Crown events are valued by some players as the most prestigious, and are also some of the oldest competitions on the professional circuit. Winning all three is a difficult challenge that has only been achieved by eleven players.
With some events having been criticised for matches taking too long, an alternative series of timed tournaments has been organised by Matchroom Sport chairman Barry Hearn. The shot-timed Premier League Snooker was established, with seven players invited to compete at regular United Kingdom venues, televised on Sky Sports. Players had twenty-five seconds to take each shot, with five time-outs per player per match. While some success was achieved with this format, it generally did not receive the same amount of press attention or status as the regular ranking tournaments. This event has been taken out of the tour since 2013, when the Champion of Champions was established. The Champion of Champions saw players qualify by virtue of winning other events in the season, with 16 champions competing.
In 2015, the World Professional Billiards and Snooker Association submitted an unsuccessful bid for snooker to be played at the 2020 Summer Olympics in Tokyo. Another bid has been put forward for 2024 Summer Olympics through the World Snooker Federation, founded in 2017. A trial for the format for cue sports to be played at the 2024 games was put forward at the 2019 World Team Trophy, also featuring nine-ball and carom billiards. Snooker has been contested at the World Games since 2001, and was included as an event at the 2019 African Games.
Several players, such as Ronnie O'Sullivan, Mark Allen and Steve Davis, have warned that there are too many tournaments during the season, and that players risk burning out. In 2012, O'Sullivan played fewer tournaments in order to spend more time with his children, and ended the 2012–13 season ranked 19th in the world. Furthermore, he did not play any tournament in 2013 except the World Championship, which he won. O'Sullivan has suggested that a "breakaway tour" with fewer events would be beneficial to the sport, but as of 2019 no such tour has been organised.
Some leagues have allowed clubs to refuse to accept women players in tournaments. League committee leadership defended the practice, saying, "If we lose two of these clubs [with the men-only policies] we would lose four teams and we can't afford to lose four teams otherwise we would have no league." A World Women's Snooker spokesperson said, "It is disappointing and unacceptable that in 2019 that players such as Rebecca Kenna have been the victim of antiquated discriminatory practices." The All-Party Parliamentary Group said, "The group believes that being prevented from playing in a club because of gender is archaic."
Non-professional snooker (including youth competition) is governed by the International Billiards and Snooker Federation (IBSF). Events held specifically for seniors are handled by the WPBSA under the World Seniors Tour. World Disability Billiards and Snooker (WDBS) is a WPBSA subsidiary that organises events and playing aids in snooker and other cue sports for people with disabilities. Snooker is a mixed gender sport that affords men and women the same opportunities to progress at all levels of the game. While the main professional tour is open to female players, there is also a separate women's tour organised by World Women's Snooker (formerly the World Ladies Billiards and Snooker Association) that encourages female players to participate in the sport.
The highest competition in the amateur sport is the IBSF World Snooker Championship, while the highest level of the senior sport is the World Seniors Championship. On the women's tour, the leading tournament is the World Women's Snooker Championship. The reigning champion is Reanne Evans who has held the women's world title twelve times since first winning the championship in 2005. Evans has also participated on the World Snooker Tour and has taken part in the qualifying rounds of the main world championship on five occasions, reaching the second round in 2017. The most prestigious amateur event in England is the English Amateur Championship, an annual competition first held in 1916, the oldest competition still being played.
In the professional era of snooker, which began with Joe Davis in the 1930s and continues until the present day, a relatively small number of players have succeeded at the top level. Davis was world champion for twenty years, retiring unbeaten after claiming his fifteenth world title in 1946 when the tournament was reinstated after the Second World War. Undefeated in World Championship play, he was only beaten four times in his life, all of these defeats coming after his retirement and inflicted by his own brother Fred Davis. He did lose matches in handicapped tournaments, but on level terms these four defeats were the only losses of his entire career. He was also world billiards champion. It is considered highly unlikely that anyone will ever dominate the game to this level again.
After Davis retired from World Championship play, the next dominant force was his younger brother Fred Davis, who had lost the 1940 final to Joe. By 1947, Fred Davis was deemed ready by his brother to take over the mantle, but lost the world final to the Scotsman Walter Donaldson. Davis and Donaldson would contest the next four finals. After the abandonment of the World Championship in 1953, with the 1952 event boycotted by British professionals, the World Professional Match-play Championship became the unofficial world championship. Fred Davis won the tournament every year from 1952 to 1956, but did not enter the 1957 event.
John Pulman was the most successful player of the 1960s, winning seven consecutive world titles between April 1964 and March 1968 when the World Championship was contested on a challenge basis, but his winning streak ended when the tournament reverted to a knockout format in 1969. Ray Reardon was the dominant force in the 1970s, winning six titles (1970, 1973–1976, and 1978), while John Spencer won three (1969, 1971, 1977).
Steve Davis won his first World Championship in 1981, becoming the 11th world champion since 1927 (including the winner of the boycotted 1952 championship, Horace Lindrum). Davis won six world titles (1981, 1983, 1984, and 1987–1989), and competed in the most-watched snooker match ever, the 1985 World Snooker Championship final with Dennis Taylor. Stephen Hendry became the 14th world champion in 1990, aged 21 years and 106 days; he is the youngest player ever to have lifted the world title. Hendry dominated the sport through the 1990s, winning the World Championship seven times (1990, 1992–1996, and 1999).
Unlike previous decades, the 21st century has produced many players of a similar standard, rather than a single player raising the bar. Ronnie O'Sullivan has come the closest to dominance in the 2000s and 2010s, having won the world title on six occasions (2001, 2004, 2008, 2012, 2013, and 2020), while John Higgins has won four times (1998, 2007, 2009, and 2011) and Mark Williams three (2000, 2003, and 2018). O'Sullivan is the only player to have made 1,000 career centuries, and holds the record for the most maximum breaks compiled in professional competition, having achieved his 15th in October 2018.
The popularity of snooker has led to the creation of many variant versions, using different rules or equipment. Variants of snooker are cue games that are based on the standard game of snooker, or similar in origin. Some have only minor rule changes and others are more distinct games. Some versions of the game, such as six-red or ten-red snooker, are played with almost identical rules but with fewer object balls, reducing the time taken to play each frame. The Six-red World Championship, contested annually in Bangkok, Thailand, has been a regular fixture on the World Snooker Tour since 2012. Popular in the women's game, ten-red had a World Women's 10-Red Championship held annually in Leeds, England, from 2017 to 2019.
Geographic variations exist in the United States and Brazil, while speed versions of the standard game have been developed in the United Kingdom. American snooker is an amateur version of the game played almost exclusively in the United States. With simplified rules and generally played on smaller tables, this variant dates back to 1925 but is now largely in decline. Sinuca brasileira (or "Brazilian snooker") is a variant of snooker played exclusively in Brazil, with fully divergent rules from the standard game, and using only one red ball instead of fifteen. At the start of the game, the single red is positioned halfway between the pink ball and the side cushion and the break-off shot cannot be used to pot the red or place the opponent in a snooker. The Snooker Shoot Out is a variant snooker tournament, first staged in 1990, featuring single-frame matches for an accelerated format. The idea was resurrected in 2011 with a modified version that was added to the professional tour in the 2010–11 season and upgraded to a ranking event in 2017.
Other games were designed with an increased number of object balls in play. One example is Snooker plus, which included two additional colours: an orange ball worth eight points positioned between pink and blue, and a purple ball worth 10 points positioned between brown and blue, increasing the maximum possible break to 210. Created by Joe Davis, and introduced at the 1959 News of the World Snooker Plus Tournament, this variant failed to gain popularity and is no longer played. Power Snooker was a short-lived cue sport based on aspects of snooker and pool, which was first played competitively as the 2010 Power Snooker Masters Trophy and again in 2011, but the format failed to gain widespread appeal and was discontinued. Using nine red balls racked in a diamond-shaped pack at the start of the game, the matches were limited to a fixed game-play period of 30 minutes. Tenball was a snooker variant designed specifically for the television show of the same name, presented by Phillip Schofield, which lasted for one series. A yellow and black ball worth ten points was added between the blue and pink, and the game had a slightly revised set of rules.