Chess annotation symbols

When annotating chess games, commentators frequently use widely recognized annotation symbols. Question marks and exclamation points that denote a move as bad or good are ubiquitous in chess literature. Some publications intended for an international audience, such as the Chess Informant, have a wide range of additional symbols that transcend language barriers.
The common symbols for evaluating the merits of a move are "??", "?", "?!", "!?", "!", and "!!". The chosen symbol is appended to the text describing the move (e.g. Re7? or Kh1!?); see Algebraic chess notation.
Use of these annotation symbols is subjective, as different annotators use the same symbols differently or for a different reason.
Move evaluation symbols, by decreasing severity or increasing effectiveness of the move:
The double question mark "??" indicates a blunder, a critically bad mistake. Typical moves that receive double question marks are those that overlook a tactic that wins substantial material or overlook a checkmate. A "??"-worthy move may result in an immediately lost position, turn a won position into a draw, lose an important piece or otherwise severely worsen the player's position. Though more common among weaker players, blunders occur at all levels of play.
A single question mark "?" indicates that the annotator thinks that the move is a mistake and should not have been played. Mistakes often lead to loss of tempo, material, or otherwise a worsening of the player's position. The nature of a mistake may be more strategic than tactical; in some cases, the move receiving a question mark may be one for which it is difficult to find a refutation. A move that overlooks a forthcoming brilliant combination from the opponent would rarely receive more than one question mark, for example. The symbol can also be used for a move that overlooks a far stronger move.
A question mark followed by an exclamation mark "?!" usually indicates that the annotator believes the move to be dubious or questionable but to possibly have merits or be difficult to refute. The "?!" may also indicate that the annotator believes the move is weak or deserves criticism but not bad enough to warrant a "?". On certain Internet chess servers, such as Chess.com and Lichess, this kind of move is marked as an "inaccuracy", denoting a weak move, appearing more regularly than with most annotators. A sacrifice leading to a dangerous attack that the opponent should be able to defend against if they play well may receive a "?!". Alternatively, this may denote a move that is objectively bad but sets up an attractive trap.
Similar to "?!" (see above), an exclamation mark followed by a question mark "!?" is one of the most controversial symbols. Different sources have slightly varying definitions, such as "interesting, but perhaps not the best move", "move deserving attention", "speculative move", "enterprising move" or "risky move". Usually it indicates that the move leads to exciting or wild play but that the objective evaluation of the move is unclear. It is also often used when a player sets a cunning trap in a lost position. Typical moves receiving a "!?" are those involving speculative sacrifices or dangerous attacks that might turn out to be unsound.
Andrew Soltis jokingly called "!?" the symbol of the lazy annotator who finds a move interesting but cannot be bothered to work out whether it is good or bad.
An exclamation point "!" indicates a good move, especially one that is surprising or requires particular skill. The symbol may also be interpreted as "best move". Annotators are usually somewhat conservative with the use of this symbol; it is not usually awarded to obvious moves that capture material or deliver checkmate.
Reasons for awarding the symbol vary greatly between annotators; among them are strong opening novelties, good psychological opening choices, well-timed breakthroughs, sound sacrifices, moves that set traps in lost positions, moves that avoid such traps, moves that punish mistakes well, sequential moves during brilliancies, and being the only good move that maintains the player's position.
The double exclamation point "!!" is used for particularly strong moves, usually difficult-to-find moves which require a high level of skill and calculation. Annotators are generally more conservative and withhold this rating more than they do the "!". Typical moves that receive a double exclamation mark include sound sacrifices of large amounts of material and counter-intuitive moves that prove very powerful. Endgame swindles sometimes receive the "!!" mark too.
For example, in what is known as the Game of the Century, there are two moves by 13-year-old Bobby Fischer which annotators typically award a double exclamation point – 11...Na4!! and 17...Be6!!, knight and queen sacrifices respectively.
The majority of chess writers and editors consider symbols more than two characters long unnecessary. However a few writers have used three or more exclamation points ("!!!") for an exceptionally brilliant move, three or more questions marks ("???") for an exceptionally bad blunder, or unusual combinations of exclamation points and question marks ("!?!", "?!?" etc) for particularly unusual, spectacular, controversial or unsound moves.
For example, when annotating Rotlewi–Rubinstein 1907, Hans Kmoch awarded Rubinstein's 22...Rxc3 three exclamation points. Annotators have also awarded the final move of Levitsky–Marshall 1912 (the "Gold Coins Game"), 23...Qg3 the "!!!" symbol.
An exceptionally bad blunder which has sometimes been awarded three or more question marks occurred in Deep Fritz–Kramnik 2006, when Kramnik played 34...Qe3, overlooking a mate in one with 35.Qh7#.
Sometimes annotation symbols are put in parentheses, e.g. "(?)", "(!)". Different writers have used these in different ways.
Ludek Pachman used "(?)" to indicate a move that he considered inferior but that he did not wish to comment on further; Simon Webb used it to indicate a move that is objectively sound, but was in his opinion a poor psychological choice; and Robert Hübner (see below) used it to indicate a move that is inaccurate and makes the player's task more difficult.
When put in parentheses, "(!)" usually indicates a subtlety which demonstrates the player's skill rather than a spectacular move.
Some writers take a less subjective or more formalized approach to these symbols.
In his 1992 book Secrets of Rook Endings and other books in the series (Secrets of Minor-Piece Endings and Secrets of Pawnless Endings), John Nunn uses these symbols in a more specific way in the context of endgames where the optimal line of play can be determined with certainty:
This convention has been used in some later works, such as Fundamental Chess Endings and Secrets of Pawn Endings by Karsten Müller and Frank Lamprecht, but it can be safely assumed the convention is not being used unless there is a specific note otherwise. The Nunn convention cannot be used to annotate full games because the exact evaluation of a position is generally impractical to compute.
In 1959, Euwe and Hooper made the same use of the question mark, "... a decisive error ...".
German grandmaster Robert Hübner prefers an even more specific and restrained use of move evaluation symbols:
When the solution to a certain chess problem is given, there are also some conventions that have become a common practice:
These symbols indicate the strategic balance of the game position:
There are other symbols used by various chess engines and publications, such as Chess Informant and Encyclopaedia of Chess Openings, when annotating moves or describing positions. Many of the symbols now have Unicode encodings, but quite a few still require a special chess font with appropriated characters.