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mime-types-data provides a registry for information about MIME media type definitions. It can be used with the Ruby mime-types library or other software 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 media types are used in MIME-compliant communications, as in e-mail or HTTP traffic, to indicate the type of content which is transmitted. The registry provided in mime-types-data contains detailed information about MIME entities. There are many types defined by RFCs and vendors, so the list is long but invariably; don't hesitate to offer additional type definitions for consideration. 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.

Data Formats Supported in this Registry

This registry contains the MIME media types in four formats:

  • A YAML format matching the Ruby mime-types library objects (MIME::Type). This is the primary user-editable format for developers. It is not shipped with the gem due to size considerations.

  • A JSON format converted from the YAML format. Prior to Ruby mime-types 3.0, this was the main consumption format and is still recommended for any implementation that does not wish to implement the columnar format, which has a significant implementation effort cost.

  • An encoded text format splitting the data for each MIME type across multiple files. This columnar data format reduces the minimal data load substantially, resulting in a performance improvement at the cost of more complex code for loading the data on-demand. This is the default format for Ruby mime-types 3.0.

  • An encoded text format for use with mini_mime (as of 3.2021.1108). This can be enabled with:

    MiniMime::Configuration.ext_db_path =
      File.join(MIME::Types::Data::PATH, "ext_mime.db")
    MiniMime::Configuration.content_type_db_path =
      File.join(MIME::Types::Data::PATH, "content_type_mime.db")

mime-types-data Modified Semantic Versioning

mime-types-data uses a heavily modified Semantic Versioning scheme to indicate that the data formats compatibility based on a SCHEMA version and the date of the data update: SCHEMA.YEAR.MONTHDAY.

  1. If an incompatible data format change is made to any of the supported formts, SCHEMA will be incremented. The current SCHEMA is 3, supporting the YAML, JSON, and columnar formats required for Ruby mime-types 3.0.

  2. When the data is updated, the YEAR.MONTHDAY combination will be updated. An update on the last day of October 2015 would be written as 2015.1031, resulting in the full version of 3.2015.1031.

  3. If multiple versions of the data need to be released on the same day due to error, there will be an additional REVISION field incremented on the end of the version. Thus, if three revisions need to be published on October 31st, 2015, the last release would be 3.2015.1031.2 (remember that the first release has an implied 0.)


MIME Type registry data



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