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MIME Types for Crystal :: A port of the Ruby MIME::Types library
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MIME Types for Crystal Build Status GitHub release Crystal Docs


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.

About MIME Media Types

MIME content types are used in MIME-compliant communications, as in e-mail or HTTP traffic, to indicate the type of content which is transmitted. The mime-types library provides the ability for detailed information about MIME entities (provided as an enumerable collection of MIME::Type objects) to be determined and used. There are many types defined by RFCs and vendors, so the list is long but by definition incomplete; don't hesitate to add additional type definitions. MIME type definitions found in mime-types are from RFCs, W3C recommendations, the IANA Media Types registry, and user contributions. It conforms to RFCs 2045 and 2231.


MIME types are used in MIME entities, as in email or HTTP traffic. It is useful at times to have information available about MIME types (or, inversely, about files). A MIME::Type stores the known information about one MIME type.

require "mime/types"

plaintext = MIME::Types["text/plain"] # => [ text/plain ]
text = plaintext.first                # => text/plain

puts text.media_type            # => "text"
puts text.sub_type              # => "plain"

puts text.extensions.join(' ')  # => "txt asc c cc h hh cpp hpp dat hlp"
puts text.preferred_extension   # => "txt"
puts text.friendly              # => "Text Document"
puts text.i18n_key              # => "text.plain"

puts text.encoding              # => quoted-printable
puts text.default_encoding      # => quoted-printable
puts text.binary?               # => false
puts text.ascii?                # => true
puts text.obsolete?             # => false
puts text.registered?           # => true
puts text.complete?             # => true

puts text                       # => "text/plain"

puts text == "text/plain"       # => true
puts "text/plain" == text       # => true
puts text == "text/x-plain"     # => false
puts "text/x-plain" == text     # => false

puts MIME::Type.simplified("x-appl/x-zip")  # => "x-appl/x-zip"
puts MIME::Type.i18n_key("x-appl/x-zip")    # => "x-appl.x-zip"

puts"text/x-plain")                   # => true
puts"x-text/x-plain")) # => true

puts text.xref_urls
# => [ "",
#      "",
#      "" ]

xtext ="x-text/x-plain")
puts xtext.media_type     # => "text"
puts xtext.raw_media_type # => "x-text"
puts xtext.sub_type       # => "plain"
puts xtext.raw_sub_type   # => "x-plain"
puts xtext.complete?      # => false

puts MIME::Types.any? { |type| type.content_type == "text/plain" }  # => true
puts MIME::Types.all?(&.registered?)                                # => false

# Various string representations of MIME types
qcelp = MIME::Types["audio/QCELP"].first  # => audio/QCELP
puts qcelp.content_type                   # => "audio/QCELP"
puts qcelp.simplified                     # => "audio/qcelp"

xwingz = MIME::Types["application/x-Wingz"].first # => application/x-Wingz
puts xwingz.content_type                          # => "application/x-Wingz"
puts xwingz.simplified                            # => "application/x-wingz"
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