Xtras are plug-in applications (alternatively known as extensions, add-ons, or
components) for Macromedia

Macromedia

Macromedia was an American graphics and web development software company headquartered in San Francisco, California that produced such products as Flash and Dreamweaver. Its rival, Adobe Systems, acquired Macromedia on December 3, 2005 and controls the line of Macromedia...

 products (now owned by Adobe

Adobe Systems

Adobe Systems Incorporated is an American computer software company founded in 1982 and headquartered in San Jose, California, United States...

), in particular Adobe Director

Adobe Director

Adobe Director is a multimedia application authoring platform created by Macromedia—now part of Adobe Systems. It allows users to build applications built on a movie metaphor, with the user as the "director" of the movie...

. They can be user-created, or bought from third party

Third-party software component

In computer programming, a third-party software component is a reusable software component developed to be either freely distributed or sold by an entity other than the original vendor of the development platform...

 vendors. Adobe maintains a list of third party Xtras. Many of Director's own functions are implemented as Xtras.

Xtras are supported and available on the following products:

• Adobe Director
  Adobe Director
  Adobe Director is a multimedia application authoring platform created by Macromedia—now part of Adobe Systems. It allows users to build applications built on a movie metaphor, with the user as the "director" of the movie...
  
   / Adobe Shockwave
• Adobe Authorware
• Adobe Freehand

Technical Aspects

Xtras use the Macromedia Open Architecture which was designed to allow easy creation of interchangeable components between Macromedia products.

Xtras for Win32 must have an .X32 file extension. Xtras for the Macintosh generally have an .XTR extension. The file extension *.X16 is reserved for Xtras for Win16.