The term tafl (Old Norse: "table", "board") (tavl) is the original name of the game. However, Hnefatafl became the preferred term for the game in Scandinavia by the end of the Viking Age, to distinguish it from other board-games, such as Skáktafl (Chess), Kvatrutafl (Tables) and Halatafl (Fox games), as these became known. The specific name Hnefatafl possibly arose as meaning "board-game of the fist", from hnefi ("fist") + tafl, where "fist" referred to the central king-piece. The precise etymology is disputed, but hnefi certainly referred to the king-piece, and several sources refer to Hnefatafl as "King's table". In Anglo-Saxon England, the term tæfl also referred to many board-games. It is not known if the Anglo-Saxons had a specific name for the game or if they generically referred to it as "tæfl" in the way that modern people might refer to "cards". In Dutch, "tafel" means "table", and in German "Tafel" has related meanings as well.
Several games may be confused with tafl games, due to the inclusion of the word "tafl" in their names or other similarities. Halatafl is the Old Norse name for Fox and Geese, a game dating from at least the 14th century. It is still known and played in Europe. Kvatrutafl is the Old Norse name for Tables (the medieval forerunner of Backgammon). Skáktafl is the Old Norse name for Chess. Fidchell or Fithcheall (Modern Irish: Ficheall) was played in Ireland. The Welsh equivalent was Gwyddbwyll and the Breton equivalent Gwezboell; all terms mean "wood-sense". This popular medieval game was played with equal forces on each side and thus was not a tafl variant, but rather may have been the medieval descendant of the Roman game Latrunculi or Ludus latrunculorum.
Hnefatafl was mentioned in several of the medieval sagas, including Orkneyinga saga, Friðþjófs saga, Hervarar saga, and others. These three period treatments of Hnefatafl offer some important clues about the game, while numerous other incidental references to Hnefatafl or Tafl exist in saga literature. In Orkeyinga saga, the notability of Hnefatafl is evident in the nine boasts of Jarl Rögnvald Kali Kolsson, who tops his list with skill at Tafl. In Friðþjófs saga, a conversation over a game of Hnefatafl reveals that the king's men are red and the attackers white, and that the word hnefi does indeed refer to the kingpiece. The most revealing – and yet most ambiguous – clues to Hnefatafl lie in a series of riddles posed by a character identified as Odin in disguise (see Gestumblindi) in Hervarar saga. One riddle, as stated in Hauksbók, refers to "the weaponless maids who fight around their lord, the [brown/red] ever sheltering and the [fair/white] ever attacking him," although there is controversy over whether the word weaponless refers to the maids or, as in other versions, to the king himself, which may support the argument that a "weaponless king" cannot take part in captures (see #Balance of play). One may also note that the assignment of the colors of brown or red to the defenders and fair or white to the attackers is consistent with Friðþjófs saga. Another of Gestumblindi's riddles asks, "What is that beast all girded with iron, which kills the flocks? He has eight horns but no head, and runs as he pleases. Here, it is the answer that is controversial, as the response has been variously translated as: "It is the húnn in hnefatafl. He has the name of a bear and runs when he is thrown;" or, "It is the húnn in hnefatafl. He has the name of a bear and escapes when he is attacked. The first problem is in translating the word húnn, which may refer to a die (as suggested by the former translation), the "eight horns" referring to the eight corners of a six-sided die and "the flocks" that he kills referring to the stakes the players lose. Alternatively, húnn may refer to the king, his "eight horns" referring to the eight defenders, which is more consistent with the latter translation, "He has the name of a bear and escapes when he is attacked. Ultimately, the literary references prove inconclusive on the use of dice in Hnefatafl.
Hnefatafl was a popular game in medieval Scandinavia and was mentioned in several of the Norse Sagas. Some of these saga references have contributed to controversy over the possible use of dice in playing hnefatafl. The rules of the game were never explicitly recorded, and only playing pieces and fragmentary boards are extant, so it is not known for sure how the game was played. If dice were in fact used, nothing has been recorded about how they were employed. Archaeological and literary sources indicate Hnefatafl may have been played on a 13×13 or an 11×11 board.
Alea evangelii, which means "game of the gospels", was described, with a drawing, in the twelfth-century Corpus Christi College, Oxford manuscript 122, from Anglo-Saxon England. It was played on the intersections of a board of 18×18 cells. The manuscript describes the layout of the board as a religious allegory, but it is clear that this was a game based on Hnefatafl.
Tawlbwrdd was played in Wales. It is described as being played with 8 pieces on the king's side and 16 on the attacker's side. Robert ap Ifan documented it with a drawing in a manuscript dated 1587. His version was played on an 11×11 board with 12 pieces on the king's side and 24 on the opponent's side. His passage states:
The above tawlbwrdd should be played with a king in the centre and twelve men in the places next to him, and twenty-four men seek to capture him. These are placed, six in the centre of each side of the board and in the six central positions. And two move the men in the game, and if one [piece] belonging to the king comes between the attackers, he is dead and is thrown out of the game, and the same if one of the attackers comes between two of the king’s men in the same manner. And if the king himself comes between two of the attackers, and if you say ‘Watch your king’ before he moves to that space, and he is unable to escape, you capture him. If the other says ‘I am your liegeman’ and goes between two, there is no harm. If the king can go along the [illegible] line, that side wins the game.
Brandub (Modern Irish: Bran dubh) was the Irish form of tafl. We know from two poems that it was played with five men against eight, and that one of the five was a "Branán", or chief. A number of 7×7 boards have been found, the most famous being the elaborate wooden board found at Ballinderry in 1932, featuring holes for pegged pieces, possibly to allow for portability of the game. The name brandub means "raven black".
Ard Ri (Irish: High King) was a Scottish tafl variant played on a 7×7 board with a king and eight defenders against sixteen attackers. This is the least documented of the known tafl variants.
Tablut, from Lapland, is the best documented version. In 1732, Carolus Linnaeus recorded the rules and a drawing of the board in his journal while travelling through the area. His description, in Latin, was incomplete, as he did not speak the Sami language of his hosts and described the game only from observing the players. The game was played on a 9×9 mat of embroidered reindeer hide. In his diary, Lachesis Lapponica, Linnaeus referred to the light (defending) pieces as "Swedes" and the dark (attacking) pieces as "Muscovites". What may have been the same game was still being played in the late nineteenth century, as described in P.A. Lindholm's Hos Lappbönder (1884).
- The game is played on a 9×9 board. Initial set-up is as shown in the diagram.
- The king starts on the central square or castle, called the konakis, which no other piece may ever occupy.
- The eight defenders, called Swedes, start on the eight squares adjoining the konakis, in the form of a cross.
- The sixteen attackers, called Muscovites, start in groups of four at the center of each edge of the board. (In Linneaus' notes, these squares were embroidered to signify them as the domain of the Muscovites.)
- All remaining squares (neutral zone) may be occupied by any piece during the game.
- Any piece may move any number of vacant spaces in any straight line [←↑→↓], but not diagonally. (Compare to the rook in Chess.)
- No piece may ever pass over another piece in its path.
- If the king should ever have an unimpeded path (through the neutral zone) to the edge of the board, unless he is immediately blocked by a Muscovite, he may escape and the game is over. (This rule suggests that the king may not escape through the domain of the Muscovites.)
- If the king should ever have a path of escape, he must call out "raichi"; if two paths of escape, then his escape is imminent and he must call out "tuichu". (Compare these to "check" and "checkmate" in Chess.)
- Any piece, save for the king, may be captured and removed from the board if it becomes surrounded on two opposite sides by enemies. (This is known as custodial capture.)
- If the king is surrounded on all four sides by enemies, he is taken prisoner. If he is surrounded on three sides, he may escape by the fourth.
- If the king is on a square adjoining the konakis and is surrounded on three sides by his enemies and the fourth by the konakis, he is captured. (This rule suggests that once the king has left the konakis, he can never return.)
- If the king is captured, the Swedes are conquered and the Muscovites victorious.
Several problems of gameplay are left woefully ambiguous or completely untouched in Linnaeus' notes, and some translations are problematic. There are also several other variations played by modern reconstructionists. More detailed information on reconstructing the rules of play can be found in this article by Sten Helmfrid.
One such solution is by bidding: Players take turns bidding on how many moves it will take them to win the game. The lowest bidder gets the king. Thus, one player may open with a bid of 15 turns, the other player may counter with a bid of 14 turns, and the first player, more confident in his ability to escape in 13 rounds than in his ability to contain for 14, may bid 13 and take the king's side. If that player does not escape within 13 turns, the other player wins. Another workaround is to play a two-round match, in which players switch sides after the first round. If the king escapes both rounds, the winner is the player whose king escaped in the fewest turns.
The description of Tawlbrydd by Robert ap Ifan (preceding Linnaeus' account by 145 years) states that the king could be captured by two men. Peterson suggests that Linnaeus' special capture of the king is incorrect, and states that statistics from modern games played with four-man capture of the king show that white wins more often than black. However, it has not yet been demonstrated that balanced play results from rules allowing for a two-man capture of the king. Interestingly, some sources indicate that Scandinavian museum reconstructions of Hnefatafl typically stipulate that the king may be captured by only two attackers unless he is still in his hall, in which case he must be surrounded on all four sides.