diff --git a/bin/webri b/bin/webri
new file mode 100755
index 0000000000..4166a2a02c
--- /dev/null
+++ b/bin/webri
@@ -0,0 +1,62 @@
+#!/usr/bin/env ruby
+
+# A console application to display Ruby HTML documentation.
+
+require 'optparse'
+require_relative '../lib/rdoc/web_ri'
+
+options = {}
+
+parser = OptionParser.new
+
+parser.version = RDoc::VERSION
+parser.banner = <<-BANNER
+webri is a console application for accessing Ruby online HTML documentation.
+
+Usage: #{parser.program_name} [options] name
+
+Argument name selects the documentation to be accessed.
+
+o If name specifies a single item, that item is selected.
+o If name specifies multiple items, those items are displayed.
+
+The given name is converted to a Regexp, which is used to select documentation.
+
+Note that your command window may require you to escape certain characters;
+in particular, you may need to escape circumflex (^), dollar sign ($),
+and pound sign (#).
+
+BANNER
+
+parser.separator('Options:')
+parser.on('-r', '--release=STR',
+          'Sets the target documentation release to STR.',
+          'If not given, uses the release of the installed Ruby',
+           "(currently #{RUBY_VERSION}).",
+          'If given and not valid, the valid releases are displayed.',
+          ) do |release|
+  options[:release] = release
+end
+parser.on('-h', '--help', 'Prints this help.') do
+  puts parser
+  exit
+end
+parser.on('-v', '--version', 'Prints the version of webri.') do
+  puts RDoc::VERSION
+  exit
+end
+parser.parse!
+
+error_message = case ARGV.size
+when 0
+  'No name given.'
+when 1
+  nil
+else
+  'Multiple names given.'
+end
+raise ArgumentError.new(error_message) if error_message
+
+target_name = ARGV.shift
+
+web_ri = RDoc::WebRI.new(target_name, options)
diff --git a/lib/rdoc/web_ri.rb b/lib/rdoc/web_ri.rb
new file mode 100644
index 0000000000..6b428cf6a1
--- /dev/null
+++ b/lib/rdoc/web_ri.rb
@@ -0,0 +1,135 @@
+# frozen_string_literal: true
+require 'rbconfig'
+require 'find'
+require 'cgi'
+
+require_relative '../rdoc'
+
+# A class to display Ruby HTML documentation.
+class RDoc::WebRI
+
+  def initialize(target_name, options)
+    ruby_exe_filepath = RbConfig.ruby
+    ruby_installation_dirpath = File.dirname(File.dirname(ruby_exe_filepath))
+    ri_filepaths = get_ri_filepaths(ruby_installation_dirpath)
+    html_filepaths = get_html_filepaths(ruby_installation_dirpath)
+    target_urls = {}
+    missing_html = []
+    unused_ri = []
+    ri_filepaths.each do |ri_filepath|
+      next if ri_filepath == 'cache.ri'
+      filepath = ri_filepath.sub('.ri', '.html')
+      name, target_url = case
+                      when filepath.match(/-c\.html/) # Class method.
+                        dirname = File.dirname(filepath)
+                        method_name = CGI.unescape(File.basename(filepath).sub('-c.html', ''))
+                        target_url = dirname + '.html#method-c-' + method_name
+                        name = dirname.gsub('/', '::') + '::' + method_name
+                        [name, target_url]
+                      when filepath.match(/-i\.html/) # Instance method.
+                        dirname = File.dirname(filepath)
+                        method_name = CGI.unescape(File.basename(filepath).sub('-i.html', ''))
+                        target_url = dirname + '.html#method-i-' + method_name
+                        name = dirname.gsub('/', '::') + '#' + method_name
+                        [name, target_url]
+                      when filepath.match(/\/cdesc-/) # Class.
+                        target_url = File.dirname(filepath) + '.html'
+                        name = target_url.gsub('/', '::').sub('.html', '')
+                        [name, target_url]
+                      when File.basename(filepath).match(/^page-/)
+                        target_url = filepath.sub('page-', '') # File.
+                        name = target_url.sub('.html', '').sub(/_rdoc$/, '.rdoc').sub(/_md$/, '.md')
+                        [name, target_url]
+                      else
+                        raise filepath
+                      end
+      unless html_filepaths.include?(target_url)
+        missing_html.push(target_url)
+        unused_ri.push(ri_filepath)
+      end
+      target_urls[name] = target_url
+    end
+    # puts missing_html.uniq
+    # puts unused_ri
+
+    selected_urls = {}
+    target_urls.select do |name, value|
+      if name.match(Regexp.new(target_name))
+        selected_urls[name] = value
+      end
+    end
+    case selected_urls.size
+    when 0
+      puts "No documentation found for #{target_name}."
+    when 1
+      url = selected_urls.first[1]
+      open_url(url)
+    else
+      p get_choice(selected_urls.keys)
+    end
+  end
+
+def get_ri_filepaths(ruby_installation_dirpath)
+  # Directory containing filetree of .ri files installed by RI.
+  ri_dirpath = File.join(ruby_installation_dirpath, 'share', 'ri', RUBY_ENGINE_VERSION, 'system')
+  ri_filepaths = []
+  Find.find(ri_dirpath).each do |path|
+    next unless path.end_with?('.ri')
+    path.sub!(ri_dirpath + '/', '')
+    ri_filepaths.push(path)
+  end
+  ri_filepaths
+  end
+
+  def get_html_filepaths(ruby_installation_dirpath)
+    # Directory containing filetree of .html files installed by RI.
+    html_dirpath = File.join(ruby_installation_dirpath, *%w[share doc ruby html])
+    filepaths = []
+    Find.find(html_dirpath).each do |path|
+      next unless path.end_with?('.html')
+      path.sub!(html_dirpath + '/', '')
+      filepaths.push(path)
+    end
+    filepaths
+  end
+
+  def get_choice(choices)
+    choices[get_choice_index(choices)]
+  end
+
+  def get_choice_index(choices)
+    index = nil
+    range = (0..choices.size - 1)
+    until range.include?(index)
+      choices.each_with_index do |choice, i|
+        s = "%6d" % i
+        puts "  #{s}:  #{choice}"
+      end
+      print "Choose (#{range}):  "
+      $stdout.flush
+      response = gets
+      index = response.match(/\d+/) ? response.to_i : -1
+    end
+    index
+  end
+
+  def open_url(target_url)
+    host_os = RbConfig::CONFIG['host_os']
+    executable_name = case host_os
+                      when /linux|bsd/
+                        'xdg-open'
+                      when /darwin/
+                        'open'
+                      when /32$/
+                        'start'
+                      else
+                        message = "Unrecognized host OS: '#{host_os}'."
+                        raise RuntimeError.new(message)
+                      end
+    command = "#{executable_name} #{target_url}"
+    p command
+    return
+    system(command)
+    end
+
+end