?

A question mark, ?, after a move says that the annotator considers it a mistake or a clearly inferior choice. The move may lose a piece, allow an attack, waste an advantage, or overlook a much stronger option.

The mark does not declare the move illegal. It describes quality according to the author's analysis, so two annotators may apply ? with different levels of severity.

Traditionally, ?? marks a much more serious error, while ?! expresses milder doubt. A program may read ? in Portable Game Notation (PGN), the plain-text game format. When saving the file in standard form, it replaces ? with $2, a dollar sign followed by the number 2.