Many Filter Operators have no parameter available. Still, each operator must be followed by a bracketed parameter expression — even if it is empty — as with the backlinks operator below:

[<currentTiddler>backlinks[]]

(Even though an expression such as [<currentTiddler>backlinks] may at first seem well-formed — insofar as closing brackets seem to pair properly with opening brackets — each operator needs its own parameter brackets, even if empty. See Filter Syntax.)

The following Filter Operators accept no parameters: