1.0.0 • Public • Published


NPM version Build status

MediumType.js is a JavaScript library to parse and stringify media types.


  • Implements parsing based on RFC 2045 with added support for suffixes (RFC 3023, RFC 6839).
    RFC 2045 is a little more permissive than later RFCs when it comes to allowed tokens. MediumType.js thereby adheres to Postel's law of liberal acceptance.

    Examples of supported media types:

    • application/json.
    • application/; charset=utf-8.
    • application/xml; dtd="".
    • */*+json; q=0.3.
    • */*.
  • Split comma separated media types (like in HTTP's Accept header).
    Note that it properly supports quoted parameters when splitting. It's the only library that I know of that does this.

    MediumType.split("text/html; levels=\"1, 2, 3\", text/plain")
  • Sort an array of MediumTypes according to sorting rules of the HTTP Accept header listed in RFC 2616 and RFC 7231.
    That is, first by the q parameter, then by type and subtype specificity and then by parameter count (excluding the q parameter).

      new MediumType("text/html; level=3; q=0.7"),
      new MediumType("text/html; q=0.7"),
      new MediumType("text/plain; q=0.5"),
      new MediumType("text/*; q=0.1"),
      new MediumType("*/*; q=0.1"),
  • Stringify media types to a canonical type/subtype+suffix; param=value format.

    MediumType.stringify({type: "application", subtype: "json"})
    new MediumType({type: "application", subtype: "json"}).toString()
  • No dependencies on Node.js modules or the whole MIME database. Pretty lightweight and easily usable in the browser with Browserify.


From v1.0.0 MediumType.js will follow semantic versioning, but until then, breaking changes may appear between minor versions (the middle number).

Installing on Node.js

npm install medium-type

Installing for the browser

MediumType.js doesn't yet have a build ready for the browser, but you will be able to use Browserify to have it run there till then.


var MediumType = require("medium-type")
var type = new MediumType("application/; charset=utf-8")
type.type == "application"
type.subtype == ""
type.suffix == "json"
type.parameters.charset == "utf-8"


For extended documentation on all functions, please see the MediumType.js API Documentation.



MediumType.js is released under a Lesser GNU Affero General Public License, which in summary means:

  • You can use this program for no cost.
  • You can use this program for both personal and commercial reasons.
  • You do not have to share your own program's code which uses this program.
  • You have to share modifications (e.g. bug-fixes) you've made to this program.

For more convoluted language, see the LICENSE file.


Andri Möll typed this and the code.
Monday Calendar supported the engineering work.

If you find MediumType.js needs improving, please don't hesitate to type to me now at or create an issue online.

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