In software engineering, extensibility is a system design principle focused on allowing an application to grow and provide additional features in the future. Web browsers are the most widespread example of system extensibility and even include bundles of additional features released as extensions, a direct nod to the design principle they are modeled after.
Extensibility should not be confused with forward compatibility, such as that seen in HTML code wherein old browsers can accept future versions of HTML without crashing. Using the same example, an HTML browser would be considered extensible if you could later add on a browser extension to handle new forms of data (including updated HTML code, image formats, and so on).
- By Jason Fitzpatrick on 12/8/13