# Marker Interfaces

A marker interface is an empty interface with no attributes, events, or methods. A marker interface is used to enable specific usage for a component in an app.

For example, a component that implements the `force:appHostable` interface can be used as a custom tab in Lightning Experience or the Salesforce mobile app.

In JavaScript, you can determine if a component implements an interface by using `myCmp.isInstanceOf("mynamespace:myinterface")`.

**See Also**

- [Configure Components for Custom Tabs](/docs/platform/aura-platform/guide/components-using-lex-s1-config-tab.md)