Various types of information and data can be, and have been, "leaked" to the Internet, the most common being personal information, computer software and source code, and artistic works such as books or albums.
For example, a musical album is leaked if it has been made available to the public on the Internet before its official release date.
There were many cases of source code leaks in the history of software development.
Sometimes software developers themselves will intentionally leak their source code in an effort to prevent a software product from becoming abandonware after it has reached its end-of-life, allowing the community to continue development and support.
Reasons for leaking instead of a proper release to public domain or as open-source can include scattered or lost intellectual property rights.