diff --git a/README.md b/README.md
index 1eebdffd..f80f0b47 100644
--- a/README.md
+++ b/README.md
@@ -88,16 +88,27 @@ specifies the number of bytes; if it is a string, the value is passed to the
 [bytes](https://www.npmjs.com/package/bytes) library for parsing. Defaults
 to `'100kb'`.
 
+##### parser
+
+The `parser` option is the function called against the request body to convert
+it to a JavaScript object. If a `reviver` is supplied, it is supplied as the
+second argument to this function.
+
+```
+parser(body, reviver) -> req.body
+```
+
+Defaults to `JSON.parse`.
+
 ##### reviver
 
-The `reviver` option is passed directly to `JSON.parse` as the second
-argument. You can find more information on this argument
+You can find more information on this argument
 [in the MDN documentation about JSON.parse](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/parse#Example.3A_Using_the_reviver_parameter).
 
 ##### strict
 
 When set to `true`, will only accept arrays and objects; when `false` will
-accept anything `JSON.parse` accepts. Defaults to `true`.
+accept anything the `parser` accepts. Defaults to `true`.
 
 ##### type
 
@@ -295,6 +306,16 @@ form. Defaults to `false`.
 
 The `depth` option is used to configure the maximum depth of the `qs` library when `extended` is `true`. This allows you to limit the amount of keys that are parsed and can be useful to prevent certain types of abuse. Defaults to `32`. It is recommended to keep this value as low as possible.
 
+##### parser
+
+The `parser` option, if supplied, is used to in place of the default parser to
+convert the request body into a JavaScript object. If this option is supplied,
+both the `extended` and `parameterLimit` options are ignored.
+
+```
+parser(body) -> req.body
+```
+
 ## Errors
 
 The middlewares provided by this module create errors using the
diff --git a/lib/factory.js b/lib/factory.js
new file mode 100644
index 00000000..356433d8
--- /dev/null
+++ b/lib/factory.js
@@ -0,0 +1,155 @@
+/*!
+ * body-parser
+ * Copyright(c) 2014 Jonathan Ong
+ * Copyright(c) 2014-2015 Douglas Christopher Wilson
+ * MIT Licensed
+ */
+
+'use strict'
+
+/**
+ * Module dependencies.
+ * @private
+ */
+
+var bytes = require('bytes')
+var contentType = require('content-type')
+var createError = require('http-errors')
+var isFinished = require('on-finished').isFinished
+var read = require('./read')
+var typeis = require('type-is')
+
+/**
+ * Module exports.
+ */
+
+module.exports = createBodyParser
+
+/**
+ * Use this to create a middleware that parses request bodies
+ *
+ * @param {function} parse
+ * @param {object} options
+ * @param {object} defaultOptions
+ * @return {function}
+ * @public
+ */
+
+function createBodyParser (parse, debug, options, defaultOptions) {
+  // Squash the options and the overrides down into one object
+  var opts = { ...defaultOptions, ...options }
+
+  var limit = typeof opts.limit !== 'number'
+    ? bytes.parse(opts.limit || '100kb')
+    : opts.limit
+  var charset = opts.charset
+  var inflate = opts.inflate !== false
+  var verify = opts.verify || false
+  var defaultReqCharset = opts.defaultCharset || 'utf-8'
+  var type = opts.type
+
+  if (verify !== false && typeof verify !== 'function') {
+    throw new TypeError('option verify must be function')
+  }
+
+  // create the appropriate type checking function
+  var shouldParse = typeof type !== 'function'
+    ? typeChecker(type)
+    : type
+
+  // create the appropriate charset validating function
+  var validCharset = typeof charset !== 'function'
+    ? charsetValidator(charset)
+    : charset
+
+  return function (req, res, next) {
+    if (isFinished(req)) {
+      debug('body already parsed')
+      next()
+      return
+    }
+
+    if (!('body' in req)) {
+      req.body = undefined
+    }
+
+    // skip requests without bodies
+    if (!typeis.hasBody(req)) {
+      debug('skip empty body')
+      next()
+      return
+    }
+
+    debug('content-type %j', req.headers['content-type'])
+
+    // determine if request should be parsed
+    if (!shouldParse(req)) {
+      debug('skip parsing')
+      next()
+      return
+    }
+
+    // assert charset per RFC 7159 sec 8.1
+    var reqCharset = null
+    if (charset !== undefined) {
+      reqCharset = getCharset(req) || defaultReqCharset
+      if (!validCharset(reqCharset)) {
+        debug('invalid charset')
+        next(createError(415, 'unsupported charset "' + reqCharset.toUpperCase() + '"', {
+          charset: reqCharset,
+          type: 'charset.unsupported'
+        }))
+        return
+      }
+    }
+
+    // read
+    read(req, res, next, parse, debug, {
+      encoding: reqCharset,
+      inflate: inflate,
+      limit: limit,
+      verify: verify
+    })
+  }
+}
+
+/**
+ * Get the charset of a request.
+ *
+ * @param {object} req
+ * @api private
+ */
+
+function getCharset (req) {
+  try {
+    return (contentType.parse(req).parameters.charset || '').toLowerCase()
+  } catch {
+    return undefined
+  }
+}
+
+/**
+ * Get the simple type checker.
+ *
+ * @param {string} type
+ * @return {function}
+ */
+
+function typeChecker (type) {
+  return function (req) {
+    return Boolean(typeis(req, type))
+  }
+}
+
+/**
+ * Get the simple charset validator.
+ *
+ * @param {string} type
+ * @return {function}
+ */
+
+function charsetValidator (charset) {
+  return function (reqCharset) {
+    return charset === reqCharset
+  }
+}
diff --git a/lib/types/json.js b/lib/types/json.js
index 30bf8cab..974ddc80 100644
--- a/lib/types/json.js
+++ b/lib/types/json.js
@@ -12,13 +12,8 @@
  * @private
  */
 
-var bytes = require('bytes')
-var contentType = require('content-type')
-var createError = require('http-errors')
 var debug = require('debug')('body-parser:json')
-var isFinished = require('on-finished').isFinished
-var read = require('../read')
-var typeis = require('type-is')
+var createBodyParser = require('../factory')
 
 /**
  * Module exports.
@@ -52,99 +47,46 @@ var JSON_SYNTAX_REGEXP = /#+/g
  */
 
 function json (options) {
-  var opts = options || {}
-
-  var limit = typeof opts.limit !== 'number'
-    ? bytes.parse(opts.limit || '100kb')
-    : opts.limit
-  var inflate = opts.inflate !== false
-  var reviver = opts.reviver
-  var strict = opts.strict !== false
-  var type = opts.type || 'application/json'
-  var verify = opts.verify || false
-
-  if (verify !== false && typeof verify !== 'function') {
-    throw new TypeError('option verify must be function')
-  }
-
-  // create the appropriate type checking function
-  var shouldParse = typeof type !== 'function'
-    ? typeChecker(type)
-    : type
-
-  function parse (body) {
-    if (body.length === 0) {
-      // special-case empty json body, as it's a common client-side mistake
-      // TODO: maybe make this configurable or part of "strict" option
-      return {}
-    }
-
-    if (strict) {
-      var first = firstchar(body)
-
-      if (first !== '{' && first !== '[') {
-        debug('strict violation')
-        throw createStrictSyntaxError(body, first)
+  var reviver = options?.reviver
+  var strict = options?.strict !== false
+  var parser = options?.parser || JSON.parse
+
+  return createBodyParser(
+    function (body) {
+      if (body.length === 0) {
+        // special-case empty json body, as it's a common client-side mistake
+        // TODO: maybe make this configurable or part of "strict" option
+        return {}
       }
-    }
-
-    try {
-      debug('parse json')
-      return JSON.parse(body, reviver)
-    } catch (e) {
-      throw normalizeJsonSyntaxError(e, {
-        message: e.message,
-        stack: e.stack
-      })
-    }
-  }
 
-  return function jsonParser (req, res, next) {
-    if (isFinished(req)) {
-      debug('body already parsed')
-      next()
-      return
-    }
-
-    if (!('body' in req)) {
-      req.body = undefined
-    }
-
-    // skip requests without bodies
-    if (!typeis.hasBody(req)) {
-      debug('skip empty body')
-      next()
-      return
-    }
+      if (strict) {
+        var first = firstchar(body)
 
-    debug('content-type %j', req.headers['content-type'])
-
-    // determine if request should be parsed
-    if (!shouldParse(req)) {
-      debug('skip parsing')
-      next()
-      return
-    }
+        if (first !== '{' && first !== '[') {
+          debug('strict violation')
+          throw createStrictSyntaxError(parser, reviver, body, first)
+        }
+      }
 
-    // assert charset per RFC 7159 sec 8.1
-    var charset = getCharset(req) || 'utf-8'
-    if (charset.slice(0, 4) !== 'utf-') {
-      debug('invalid charset')
-      next(createError(415, 'unsupported charset "' + charset.toUpperCase() + '"', {
-        charset: charset,
-        type: 'charset.unsupported'
-      }))
-      return
+      try {
+        debug('parse json')
+        return parser(body, reviver)
+      } catch (e) {
+        throw normalizeJsonSyntaxError(e, {
+          message: e.message,
+          stack: e.stack
+        })
+      }
+    },
+    debug,
+    options,
+    {
+      type: 'application/json',
+      charset: function (charset) {
+        return charset.slice(0, 4) === 'utf-'
+      }
     }
-
-    // read
-    read(req, res, next, parse, debug, {
-      encoding: charset,
-      inflate: inflate,
-      limit: limit,
-      verify: verify
-    })
-  }
+  )
 }
 
 /**
@@ -156,7 +98,7 @@ function json (options) {
  * @private
  */
 
-function createStrictSyntaxError (str, char) {
+function createStrictSyntaxError (parser, reviver, str, char) {
   var index = str.indexOf(char)
   var partial = ''
 
@@ -169,7 +111,7 @@ function createStrictSyntaxError (str, char) {
   }
 
   try {
-    JSON.parse(partial); /* istanbul ignore next */ throw new SyntaxError('strict violation')
+    parser(partial, reviver); /* istanbul ignore next */ throw new SyntaxError('strict violation')
   } catch (e) {
     return normalizeJsonSyntaxError(e, {
       message: e.message.replace(JSON_SYNTAX_REGEXP, function (placeholder) {
@@ -196,21 +138,6 @@ function firstchar (str) {
     : undefined
 }
 
-/**
- * Get the charset of a request.
- *
- * @param {object} req
- * @api private
- */
-
-function getCharset (req) {
-  try {
-    return (contentType.parse(req).parameters.charset || '').toLowerCase()
-  } catch (e) {
-    return undefined
-  }
-}
-
 /**
  * Normalize a SyntaxError for JSON.parse.
  *
@@ -235,16 +162,3 @@ function normalizeJsonSyntaxError (error, obj) {
 
   return error
 }
-
-/**
- * Get the simple type checker.
- *
- * @param {string} type
- * @return {function}
- */
-
-function typeChecker (type) {
-  return function checkType (req) {
-    return Boolean(typeis(req, type))
-  }
-}
diff --git a/lib/types/raw.js b/lib/types/raw.js
index bfe274cf..232d4aa2 100644
--- a/lib/types/raw.js
+++ b/lib/types/raw.js
@@ -10,11 +10,8 @@
  * Module dependencies.
  */
 
-var bytes = require('bytes')
 var debug = require('debug')('body-parser:raw')
-var isFinished = require('on-finished').isFinished
-var read = require('../read')
-var typeis = require('type-is')
+var createBodyParser = require('../factory')
 
 /**
  * Module exports.
@@ -31,74 +28,10 @@ module.exports = raw
  */
 
 function raw (options) {
-  var opts = options || {}
-
-  var inflate = opts.inflate !== false
-  var limit = typeof opts.limit !== 'number'
-    ? bytes.parse(opts.limit || '100kb')
-    : opts.limit
-  var type = opts.type || 'application/octet-stream'
-  var verify = opts.verify || false
-
-  if (verify !== false && typeof verify !== 'function') {
-    throw new TypeError('option verify must be function')
-  }
-
-  // create the appropriate type checking function
-  var shouldParse = typeof type !== 'function'
-    ? typeChecker(type)
-    : type
-
-  function parse (buf) {
-    return buf
-  }
-
-  return function rawParser (req, res, next) {
-    if (isFinished(req)) {
-      debug('body already parsed')
-      next()
-      return
-    }
-
-    if (!('body' in req)) {
-      req.body = undefined
-    }
-
-    // skip requests without bodies
-    if (!typeis.hasBody(req)) {
-      debug('skip empty body')
-      next()
-      return
-    }
-
-    debug('content-type %j', req.headers['content-type'])
-
-    // determine if request should be parsed
-    if (!shouldParse(req)) {
-      debug('skip parsing')
-      next()
-      return
-    }
-
-    // read
-    read(req, res, next, parse, debug, {
-      encoding: null,
-      inflate: inflate,
-      limit: limit,
-      verify: verify
-    })
-  }
-}
-
-/**
- * Get the simple type checker.
- *
- * @param {string} type
- * @return {function}
- */
-
-function typeChecker (type) {
-  return function checkType (req) {
-    return Boolean(typeis(req, type))
-  }
+  return createBodyParser(
+    function (buf) { return buf },
+    debug,
+    options,
+    { type: 'application/octet-stream' }
+  )
 }
diff --git a/lib/types/text.js b/lib/types/text.js
index b153931b..43707dcf 100644
--- a/lib/types/text.js
+++ b/lib/types/text.js
@@ -10,12 +10,8 @@
  * Module dependencies.
  */
 
-var bytes = require('bytes')
-var contentType = require('content-type')
 var debug = require('debug')('body-parser:text')
-var isFinished = require('on-finished').isFinished
-var read = require('../read')
-var typeis = require('type-is')
+var createBodyParser = require('../factory')
 
 /**
  * Module exports.
@@ -32,93 +28,14 @@ module.exports = text
  */
 
 function text (options) {
-  var opts = options || {}
-
-  var defaultCharset = opts.defaultCharset || 'utf-8'
-  var inflate = opts.inflate !== false
-  var limit = typeof opts.limit !== 'number'
-    ? bytes.parse(opts.limit || '100kb')
-    : opts.limit
-  var type = opts.type || 'text/plain'
-  var verify = opts.verify || false
-
-  if (verify !== false && typeof verify !== 'function') {
-    throw new TypeError('option verify must be function')
-  }
-
-  // create the appropriate type checking function
-  var shouldParse = typeof type !== 'function'
-    ? typeChecker(type)
-    : type
-
-  function parse (buf) {
-    return buf
-  }
-
-  return function textParser (req, res, next) {
-    if (isFinished(req)) {
-      debug('body already parsed')
-      next()
-      return
-    }
-
-    if (!('body' in req)) {
-      req.body = undefined
+  return createBodyParser(
+    function (buf) { return buf },
+    debug,
+    options,
+    {
+      type: 'text/plain',
+      charset: function () { return true },
+      defaultCharset: 'utf-8'
     }
-
-    // skip requests without bodies
-    if (!typeis.hasBody(req)) {
-      debug('skip empty body')
-      next()
-      return
-    }
-
-    debug('content-type %j', req.headers['content-type'])
-
-    // determine if request should be parsed
-    if (!shouldParse(req)) {
-      debug('skip parsing')
-      next()
-      return
-    }
-
-    // get charset
-    var charset = getCharset(req) || defaultCharset
-
-    // read
-    read(req, res, next, parse, debug, {
-      encoding: charset,
-      inflate: inflate,
-      limit: limit,
-      verify: verify
-    })
-  }
-}
-
-/**
- * Get the charset of a request.
- *
- * @param {object} req
- * @api private
- */
-
-function getCharset (req) {
-  try {
-    return (contentType.parse(req).parameters.charset || '').toLowerCase()
-  } catch (e) {
-    return undefined
-  }
-}
-
-/**
- * Get the simple type checker.
- *
- * @param {string} type
- * @return {function}
- */
-
-function typeChecker (type) {
-  return function checkType (req) {
-    return Boolean(typeis(req, type))
-  }
+  )
 }
diff --git a/lib/types/urlencoded.js b/lib/types/urlencoded.js
index 687745f8..2e0de844 100644
--- a/lib/types/urlencoded.js
+++ b/lib/types/urlencoded.js
@@ -12,14 +12,10 @@
  * @private
  */
 
-var bytes = require('bytes')
-var contentType = require('content-type')
 var createError = require('http-errors')
 var debug = require('debug')('body-parser:urlencoded')
-var isFinished = require('on-finished').isFinished
-var read = require('../read')
-var typeis = require('type-is')
 var qs = require('qs')
+var createBodyParser = require('../factory')
 
 /**
  * Module exports.
@@ -34,107 +30,39 @@ module.exports = urlencoded
  * @return {function}
  * @public
  */
-
 function urlencoded (options) {
-  var opts = options || {}
-
-  var extended = Boolean(opts.extended)
-  var inflate = opts.inflate !== false
-  var limit = typeof opts.limit !== 'number'
-    ? bytes.parse(opts.limit || '100kb')
-    : opts.limit
-  var type = opts.type || 'application/x-www-form-urlencoded'
-  var verify = opts.verify || false
-  var charsetSentinel = opts.charsetSentinel
-  var interpretNumericEntities = opts.interpretNumericEntities
-
-  if (verify !== false && typeof verify !== 'function') {
-    throw new TypeError('option verify must be function')
-  }
-
-  var defaultCharset = opts.defaultCharset || 'utf-8'
-  if (defaultCharset !== 'utf-8' && defaultCharset !== 'iso-8859-1') {
-    throw new TypeError('option defaultCharset must be either utf-8 or iso-8859-1')
-  }
-
-  // create the appropriate query parser
-  var queryparse = createQueryParser(opts, extended)
-
-  // create the appropriate type checking function
-  var shouldParse = typeof type !== 'function'
-    ? typeChecker(type)
-    : type
-
-  function parse (body, encoding) {
-    return body.length
-      ? queryparse(body, encoding)
-      : {}
-  }
-
-  return function urlencodedParser (req, res, next) {
-    if (isFinished(req)) {
-      debug('body already parsed')
-      next()
-      return
-    }
-
-    if (!('body' in req)) {
-      req.body = undefined
-    }
-
-    // skip requests without bodies
-    if (!typeis.hasBody(req)) {
-      debug('skip empty body')
-      next()
-      return
-    }
-
-    debug('content-type %j', req.headers['content-type'])
-
-    // determine if request should be parsed
-    if (!shouldParse(req)) {
-      debug('skip parsing')
-      next()
-      return
-    }
-
-    // assert charset
-    var charset = getCharset(req) || defaultCharset
-    if (charset !== 'utf-8' && charset !== 'iso-8859-1') {
-      debug('invalid charset')
-      next(createError(415, 'unsupported charset "' + charset.toUpperCase() + '"', {
-        charset: charset,
-        type: 'charset.unsupported'
-      }))
-      return
+  var extended = Boolean(options?.extended)
+  var parser = options?.parser || createQueryParser(options, extended)
+
+  return createBodyParser(
+    function (body, encoding) {
+      return body.length ? parser(body, encoding) : {}
+    },
+    debug,
+    options,
+    {
+      type: 'application/x-www-form-urlencoded',
+      charset: function (charset) {
+        return charset === 'utf-8' || charset === 'iso-8859-1'
+      }
     }
-
-    // read
-    read(req, res, next, parse, debug, {
-      debug: debug,
-      encoding: charset,
-      inflate: inflate,
-      limit: limit,
-      verify: verify,
-      charsetSentinel: charsetSentinel,
-      interpretNumericEntities: interpretNumericEntities
-    })
-  }
+  )
 }
 
 /**
  * Get the extended query parser.
  *
  * @param {object} options
+ * @return {function}
  */
 
 function createQueryParser (options, extended) {
-  var parameterLimit = options.parameterLimit !== undefined
+  var parameterLimit = options?.parameterLimit !== undefined
     ? options.parameterLimit
     : 1000
-  var charsetSentinel = options.charsetSentinel
-  var interpretNumericEntities = options.interpretNumericEntities
-  var depth = extended ? (options.depth !== undefined ? options.depth : 32) : 0
+  var charsetSentinel = options?.charsetSentinel
+  var interpretNumericEntities = options?.interpretNumericEntities
+  var depth = extended ? (options?.depth !== undefined ? options.depth : 32) : 0
 
   if (isNaN(parameterLimit) || parameterLimit < 1) {
     throw new TypeError('option parameterLimit must be a positive number')
@@ -184,21 +112,6 @@ function createQueryParser (options, extended) {
   }
 }
 
-/**
- * Get the charset of a request.
- *
- * @param {object} req
- * @api private
- */
-
-function getCharset (req) {
-  try {
-    return (contentType.parse(req).parameters.charset || '').toLowerCase()
-  } catch (e) {
-    return undefined
-  }
-}
-
 /**
  * Count the number of parameters, stopping once limit reached
  *
@@ -222,16 +135,3 @@ function parameterCount (body, limit) {
 
   return count
 }
-
-/**
- * Get the simple type checker.
- *
- * @param {string} type
- * @return {function}
- */
-
-function typeChecker (type) {
-  return function checkType (req) {
-    return Boolean(typeis(req, type))
-  }
-}
diff --git a/test/json.js b/test/json.js
index 3b5cc653..642c30b1 100644
--- a/test/json.js
+++ b/test/json.js
@@ -94,6 +94,18 @@ describe('bodyParser.json()', function () {
       .expect(200, '{"user":"tobi"}', done)
   })
 
+  it('should use external parsers', function (done) {
+    request(createServer({
+      parser: function (body) {
+        return { foo: 'bar' }
+      }
+    }))
+      .post('/')
+      .set('Content-Type', 'application/json')
+      .send('{"str":')
+      .expect(200, '{"foo":"bar"}', done)
+  })
+
   describe('when JSON is invalid', function () {
     before(function () {
       this.server = createServer()
diff --git a/test/urlencoded.js b/test/urlencoded.js
index dfe0eb9f..e11fe8fa 100644
--- a/test/urlencoded.js
+++ b/test/urlencoded.js
@@ -20,6 +20,16 @@ describe('bodyParser.urlencoded()', function () {
       .expect(200, '{"user":"tobi"}', done)
   })
 
+  it('should parse x-www-form-urlencoded with custom parser', function (done) {
+    request(createServer({
+      parser: function (input) { return input.toUpperCase() }
+    }))
+      .post('/')
+      .set('Content-Type', 'application/x-www-form-urlencoded')
+      .send('user=tobi')
+      .expect(200, '"USER=TOBI"', done)
+  })
+
   it('should 400 when invalid content-length', function (done) {
     var urlencodedParser = bodyParser.urlencoded()
     var server = createServer(function (req, res, next) {