CodeQL documentation

Lexical syntax

The QL syntax includes different kinds of keywords, identifiers, and comments.

For an overview of the lexical syntax, see “Lexical syntax” in the QL language specification.


All standard one-line and multiline comments are ignored by the QL compiler and are only visible in the source code. You can also write another kind of comment, namely QLDoc comments. These comments describe QL entities and are displayed as pop-up information in QL editors.

The following example uses these three different kinds of comments:

 * A QLDoc comment that describes the class `Digit`.
class Digit extends int {  // A short one-line comment
  Digit() {
    this in [0 .. 9]

  A standard multiline comment, perhaps to provide
  additional details, or to write a TODO comment.
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