The mime-types library provides a library and registry for information
about MIME content type definitions. It can be used to determine
defined filename extensions for MIME types, or to use filename
extensions to look up the likely MIME type definitions. Version 3.0 is
a major release that requires Ruby 2.0 compatibility and removes
deprecated functions. The columnar registry format introduced in 2.6
has been made the primary format; the registry data has been extracted
from this library and put into the rubygem-mime-types-data package.
Additionally, mime-types is now licensed exclusively under the MIT
licence and there is a code of conduct in effect. There are a number of
other smaller changes described in the History file.