The marker interface pattern is a design pattern in computer science.
This pattern allows a class to implement a marker interface, which exposes some underlying semantic property of the class that cannot be determined solely by the class' methods. Whereas a typical interface specifies functionality (in the form of method declarations) that an implementing class must support, a marker interface need not do so. The mere presence of such an interface indicates specific behavior on the part of the implementing class. Hybrid interfaces, which both act as markers and specify required methods, are possible but may prove confusing if improperly used.
One good example of a marker interface comes from the Java programming language. The Cloneable interface should be implemented by a class if it fully supports the Object.clone() method. Every class in Java has the Object class at the root of its inheritance hierarchy and so every object instantiated from any class has an associated clone() method. However, developers should only call clone() on objects of classes which implement the Clonable interface, as it indicates that the cloning functionality is actually supported in a proper manner.