Wine is a free software application that aims to allow Unix-like computer operating systems to execute programs written for Microsoft Windows. Wine also provides a software library known as Winelib against which developers can compile Windows applications to help port them to Unix-like systems.

Wine is predominantly written by means of enhanced “clean-room” techniques, with some developers advising against the use of certain information obtained via documentation or tools present in proprietary SDKs (for example, the Platform SDK or Windows Driver Kit). In most circumstances Wine developers use black-box testing to uncover specific behaviour, and code added to Wine is generally required to be accompanied by test cases.

The project lead is Alexandre Julliard.