In programming, a selector is an operation that returns the state of an object--defining characteristics pertaining to the object--without altering that state. Typical selector operations begin with the command "get." Methods or procedures that can modify the object state, which are called modifiers, typically begin with the command "set."

Selectors are widely used in a number of programming languages. In a context-sensitive language like HTML, selectors match the desired pattern to the element that produces the pattern. Here, selectors are tags that specify what is to be achieved with a target block of text. A variety of selectors exist to fulfill these requirements. Contextual selectors are used when styles should be applied to an element under specific circumstances, such as specifying when a portion of text is to be blocked and manipulated in some manner, as in bolding or underlining. Other text styles, such as the size and colors of a portion of text, is specified by an alpha-numeric ID selector. Various styles can be grouped into classes. A class can be specified using a type of selector termed a class selector.

In the Java programming language, other selectors that are termed data selectors function in providing various options for the display of retrieved source data. Four selectors can be invoked at a time, which aids a user in extracting the maximum amount of information from data.