URI is a module providing classes to handle Uniform Resource Identifiers (RFC2396).


  • Uniform way of handling URIs.

  • Flexibility to introduce custom URI schemes.

  • Flexibility to have an alternate URI::Parser (or just different patterns and regexp’s).

Basic example

require 'uri'

uri = URI("http://foo.com/posts?id=30&limit=5#time=1305298413")
#=> #<URI::HTTP http://foo.com/posts?id=30&limit=5#time=1305298413>

uri.scheme    #=> "http"
uri.host      #=> "foo.com"
uri.path      #=> "/posts"
uri.query     #=> "id=30&limit=5"
uri.fragment  #=> "time=1305298413"

uri.to_s      #=> "http://foo.com/posts?id=30&limit=5#time=1305298413"

Adding custom URIs

module URI
  class RSYNC < Generic
    DEFAULT_PORT = 873
  register_scheme 'RSYNC', RSYNC

#=> {"FILE"=>URI::File, "FTP"=>URI::FTP, "HTTP"=>URI::HTTP,
#    "MAILTO"=>URI::MailTo, "RSYNC"=>URI::RSYNC}

uri = URI("rsync://rsync.foo.com")
#=> #<URI::RSYNC rsync://rsync.foo.com>

RFC References

A good place to view an RFC spec is www.ietf.org/rfc.html.

Here is a list of all related RFC’s:

Class tree

Copyright Info


Akira Yamada <akira@ruby-lang.org>


Akira Yamada <akira@ruby-lang.org> Dmitry V. Sabanin <sdmitry@lrn.ru> Vincent Batts <vbatts@hashbangbash.com>


Copyright © 2001 akira yamada <akira@ruby-lang.org> You can redistribute it and/or modify it under the same term as Ruby.

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curl https://encoding.spec.whatwg.org/encodings.json|
ruby -rjson -e 'H={}
  Encoding.find(n=h.fetch(n=x["name"].downcase,n))rescue next
puts "{"
H.each{|k,v|puts %[  #{k.dump}=>#{v.dump},]}
puts "}"

Class Methods
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Like URI.decode_www_form_component, except that '+' is preserved.

Returns name/value pairs derived from the given string str, which must be an ASCII string.

The method may be used to decode the body of Net::HTTPResponse object res for which res['Content-Type'] is 'application/x-www-form-urlencoded'.

The returned data is an array of 2-element subarrays; each subarray is a name/value pair (both are strings). Each returned string has encoding enc, and has had invalid characters removed via String#scrub.

A simple example:

# => [["foo", "0"], ["bar", "1"], ["baz", ""]]

The returned strings have certain conversions, similar to those performed in URI.decode_www_form_component:

# => [["f#o", "/"], ["b-r", "$"], ["b z", "@"]]

The given string may contain consecutive separators:

# => [["foo", "0"], ["", ""], ["bar", "1"], ["", ""], ["baz", "2"]]

A different separator may be specified:

URI.decode_www_form('foo=0--bar=1--baz', separator: '--')
# => [["foo", "0"], ["bar", "1"], ["baz", ""]]

Returns a string decoded from the given URL-encoded string str.

The given string is first encoded as Encoding::ASCII-8BIT (using String#b), then decoded (as below), and finally force-encoded to the given encoding enc.

The returned string:

  • Preserves:

    • Characters '*', '.', '-', and '_'.

    • Character in ranges 'a'..'z', 'A'..'Z', and '0'..'9'.


    # => "*.-_azAZ09"
  • Converts:

    • Character '+' to character ' '.

    • Each “percent notation” to an ASCII character.


    # => "Here are some punctuation characters: ,;?:"

Related: URI.decode_uri_component (preserves '+').

Like URI.encode_www_form_component, except that ' ' (space) is encoded as '%20' (instead of '+').

Returns a URL-encoded string derived from the given Enumerable enum.

The result is suitable for use as form data for an HTTP request whose Content-Type is 'application/x-www-form-urlencoded'.

The returned string consists of the elements of enum, each converted to one or more URL-encoded strings, and all joined with character '&'.

Simple examples:

URI.encode_www_form([['foo', 0], ['bar', 1], ['baz', 2]])
# => "foo=0&bar=1&baz=2"
URI.encode_www_form({foo: 0, bar: 1, baz: 2})
# => "foo=0&bar=1&baz=2"

The returned string is formed using method URI.encode_www_form_component, which converts certain characters:

URI.encode_www_form('f#o': '/', 'b-r': '$', 'b z': '@')
# => "f%23o=%2F&b-r=%24&b+z=%40"

When enum is Array-like, each element ele is converted to a field:

  • If ele is an array of two or more elements, the field is formed from its first two elements (and any additional elements are ignored):

    name = URI.encode_www_form_component(ele[0], enc)
    value = URI.encode_www_form_component(ele[1], enc)


    URI.encode_www_form([%w[foo bar], %w[baz bat bah]])
    # => "foo=bar&baz=bat"
    URI.encode_www_form([['foo', 0], ['bar', :baz, 'bat']])
    # => "foo=0&bar=baz"
  • If ele is an array of one element, the field is formed from ele[0]:



    URI.encode_www_form([['foo'], [:bar], [0]])
    # => "foo&bar&0"
  • Otherwise the field is formed from ele:



    URI.encode_www_form(['foo', :bar, 0])
    # => "foo&bar&0"

The elements of an Array-like enum may be mixture:

URI.encode_www_form([['foo', 0], ['bar', 1, 2], ['baz'], :bat])
# => "foo=0&bar=1&baz&bat"

When enum is Hash-like, each key/value pair is converted to one or more fields:

  • If value is Array-convertible, each element ele in value is paired with key to form a field:

    name = URI.encode_www_form_component(key, enc)
    value = URI.encode_www_form_component(ele, enc)


    URI.encode_www_form({foo: [:bar, 1], baz: [:bat, :bam, 2]})
    # => "foo=bar&foo=1&baz=bat&baz=bam&baz=2"
  • Otherwise, key and value are paired to form a field:

    name = URI.encode_www_form_component(key, enc)
    value = URI.encode_www_form_component(value, enc)


    URI.encode_www_form({foo: 0, bar: 1, baz: 2})
    # => "foo=0&bar=1&baz=2"

The elements of a Hash-like enum may be mixture:

URI.encode_www_form({foo: [0, 1], bar: 2})
# => "foo=0&foo=1&bar=2"

Returns a URL-encoded string derived from the given string str.

The returned string:

  • Preserves:

    • Characters '*', '.', '-', and '_'.

    • Character in ranges 'a'..'z', 'A'..'Z', and '0'..'9'.


    # => "*.-_azAZ09"
  • Converts:

    • Character ' ' to character '+'.

    • Any other character to “percent notation”; the percent notation for character c is '%%%X' % c.ord.


    URI.encode_www_form_component('Here are some punctuation characters: ,;?:')
    # => "Here+are+some+punctuation+characters%3A+%2C%3B%3F%3A"


  • If str has encoding Encoding::ASCII_8BIT, argument enc is ignored.

  • Otherwise str is converted first to Encoding::UTF_8 (with suitable character replacements), and then to encoding enc.

In either case, the returned string has forced encoding Encoding::US_ASCII.

Related: URI.encode_uri_component (encodes ' ' as '%20').

Returns a new object constructed from the given scheme, arguments, and default:

  • The new object is an instance of URI.scheme_list[scheme.upcase].

  • The object is initialized by calling the class initializer using scheme and arguments. See URI::Generic.new.


values = ['john.doe', 'www.example.com', '123', nil, '/forum/questions/', nil, 'tag=networking&order=newest', 'top']
URI.for('https', *values)
# => #<URI::HTTPS https://john.doe@www.example.com:123/forum/questions/?tag=networking&order=newest#top>
URI.for('foo', *values, default: URI::HTTP)
# => #<URI::HTTP foo://john.doe@www.example.com:123/forum/questions/?tag=networking&order=newest#top>

Merges the given URI strings str per RFC 2396.

Each string in str is converted to an RFC3986 URI before being merged.


# => #<URI::HTTP http://example.com/main.rbx>

URI.join('http://example.com', 'foo')
# => #<URI::HTTP http://example.com/foo>

URI.join('http://example.com', '/foo', '/bar')
# => #<URI::HTTP http://example.com/bar>

URI.join('http://example.com', '/foo', 'bar')
# => #<URI::HTTP http://example.com/bar>

URI.join('http://example.com', '/foo/', 'bar')
# => #<URI::HTTP http://example.com/foo/bar>

Allows the opening of various resources including URIs.

If the first argument responds to the ‘open’ method, ‘open’ is called on it with the rest of the arguments.

If the first argument is a string that begins with (protocol)://, it is parsed by URI.parse. If the parsed object responds to the ‘open’ method, ‘open’ is called on it with the rest of the arguments.

Otherwise, Kernel#open is called.

OpenURI::OpenRead#open provides URI::HTTP#open, URI::HTTPS#open and URI::FTP#open, Kernel#open.

We can accept URIs and strings that begin with http://, https:// and ftp://. In these cases, the opened file object is extended by OpenURI::Meta.

Returns a new URI object constructed from the given string uri:

# => #<URI::HTTPS https://john.doe@www.example.com:123/forum/questions/?tag=networking&order=newest#top>
# => #<URI::HTTP http://john.doe@www.example.com:123/forum/questions/?tag=networking&order=newest#top>

It’s recommended to first ::escape string uri if it may contain invalid URI characters.

Registers the given klass as the class to be instantiated when parsing a URI with the given scheme:

URI.register_scheme('MS_SEARCH', URI::Generic) # => URI::Generic
URI.scheme_list['MS_SEARCH']                   # => URI::Generic

Note that after calling String#upcase on scheme, it must be a valid constant name.

Returns a hash of the defined schemes:

# =>

Related: URI.register_scheme.

Returns a 9-element array representing the parts of the URI formed from the string uri; each array element is a string or nil:

names = %w[scheme userinfo host port registry path opaque query fragment]
values = URI.split('https://john.doe@www.example.com:123/forum/questions/?tag=networking&order=newest#top')
# =>
[["scheme", "https"],
 ["userinfo", "john.doe"],
 ["host", "www.example.com"],
 ["port", "123"],
 ["registry", nil],
 ["path", "/forum/questions/"],
 ["opaque", nil],
 ["query", "tag=networking&order=newest"],
 ["fragment", "top"]]