  Researchers generally place the most trust in peer-reviewed, published
information, such as journals and conference papers. By contrast, software
engineering (SE) practitioners typically do not have the time, access or
expertise to review and benefit from such publications. As a result,
practitioners are more likely to turn to other sources of information that they
trust, e.g., trade magazines, online blog-posts, survey results or technical
reports, collectively referred to as Grey Literature (GL). Furthermore,
practitioners also share their ideas and experiences as GL, which can serve as
a valuable data source for research. While GL itself is not a new topic in SE,
using, benefitting and synthesizing knowledge from the GL in SE is a
contemporary topic in empirical SE research and we are seeing that researchers
are increasingly benefitting from the knowledge available within GL. The goal
of this chapter is to provide an overview to GL in SE, together with insights
on how SE researchers can effectively use and benefit from the knowledge and
evidence available in the vast amount of GL.
