diff --git a/Gemfile b/Gemfile
index 16d6317c..187ae8a8 100644
--- a/Gemfile
+++ b/Gemfile
@@ -2,11 +2,14 @@ source "https://rubygems.org"
 
 gem "rails", "~> 4.0.0"
 gem "rails-observers"
+
+gem "coffee-rails", "~> 4.0.0"
+gem "coffee-rails-source-maps", :group => :development
 gem "jquery-rails"
+gem "jquery-ui-rails"
+gem "uglifier"
 
 gem "sass-rails"
-gem "uglifier"
-gem "jquery-ui-rails"
 
 gem "pg", :platforms => [:ruby, :mswin, :mingw]
 gem "activerecord-jdbcpostgresql-adapter", "~> 1.3.0.rc1", :platforms => :jruby
diff --git a/Gemfile.lock b/Gemfile.lock
index eacbe037..c8f25a73 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -42,6 +42,15 @@ GEM
     cache_digests (0.3.1)
       actionpack (>= 3.2)
       thread_safe
+    coffee-rails (4.0.1)
+      coffee-script (>= 2.2.0)
+      railties (>= 4.0.0, < 5.0)
+    coffee-rails-source-maps (1.4.0)
+      coffee-script-source (>= 1.6.1)
+    coffee-script (2.2.0)
+      coffee-script-source
+      execjs
+    coffee-script-source (1.7.0)
     daemons (1.1.9)
     dalli (2.7.0)
     diff-lcs (1.2.5)
@@ -178,6 +187,8 @@ DEPENDENCIES
   acts_as_versioned_rails3
   addressable
   cache_digests
+  coffee-rails (~> 4.0.0)
+  coffee-rails-source-maps
   daemons
   dalli
   diff-lcs
diff --git a/app/assets/javascripts/boot.js.coffee b/app/assets/javascripts/boot.js.coffee
new file mode 100644
index 00000000..8e5d7663
--- /dev/null
+++ b/app/assets/javascripts/boot.js.coffee
@@ -0,0 +1,4 @@
+#= require moebooru
+#= require moebooru/related_tags
+jQuery(document).ready ->
+  Moebooru.relatedTags.initialize()
diff --git a/app/assets/javascripts/moebooru/related_tags.js.coffee b/app/assets/javascripts/moebooru/related_tags.js.coffee
new file mode 100644
index 00000000..34803e6a
--- /dev/null
+++ b/app/assets/javascripts/moebooru/related_tags.js.coffee
@@ -0,0 +1,121 @@
+#= require moebooru
+jQuery(document).ready ($) ->
+  window.Moebooru.relatedTags =
+    recentTags: -> $.cookie("recent_tags").match(/\S+/g) || []
+    myTags: -> $.cookie("my_tags").match(/\S+/g) || []
+    artistSource: -> $("#post_source").val()
+    source: -> $ "#post_tags"
+    target: -> $ "#related"
+    tagUrl: (tag) -> Moebooru.path "/post?tags=#{encodeURIComponent tag}"
+
+    getTags: ->
+      source = @source()
+      selectFrom = source[0].selectionStart
+      selectTo = source[0].selectionEnd
+      tags = source.val()
+
+      if tags.length != 0 && selectFrom != 0 && selectFrom != tags.length
+        selectionStart = tags.slice(0, selectFrom).lastIndexOf " "
+        selectionEnd = tags.indexOf " ", selectTo
+        selectionStart = 0 if selectionStart == -1
+        selectionEnd = undefined if selectionEnd == -1
+        tags = tags.slice selectionStart, selectionEnd
+      tags
+
+    refreshList: (extra) ->
+      buf = @target().empty()
+      if @myTags().length > 0
+        buf.append @buildList("My Tags", @myTags())
+      if @recentTags().length > 0
+        buf.append @buildList("Recent Tags", @recentTags())
+
+      for title, tags of extra
+        buf.append @buildList(title, tags) if tags.length > 0
+
+      @highlightList()
+
+    highlightList: ->
+      highlightedTags = @source().val().match(/\S+/g) || []
+      $(".tag-column").find("a").removeClass "highlighted"
+      for tag in highlightedTags
+        $(".tag-column").find("a[href='#{@tagUrl tag}']").addClass "highlighted"
+
+    buildList: (title, tags) ->
+      buf = $("<div>").addClass "tag-column"
+      buf.append $("<h6>").text(title.replace /_/g, " ")
+      tagsList = $("<ul>")
+
+      for tag in tags.sort()
+        tagName = tag.replace /_/g, " "
+        tag = tag
+        tagsList.append(
+          $("<li>").append $("<a>").text(tagName).attr(href: @tagUrl(tag))
+        )
+
+      buf.append tagsList
+
+    fetchStart: -> @target().html $("<em>").text("Fetching...")
+
+    fetchArtistSuccess: (data) ->
+      console.log (artist.name for artist in data)
+      @refreshList "Artist": (artist.name for artist in data)
+
+    fetchSuccess: (data) ->
+      tagsCollection = {}
+      for name, tags of data
+        tagsCollection[name] = (tag[0] for tag in tags)
+      @refreshList tagsCollection
+
+    toggleTag: (e) ->
+      e.preventDefault()
+      tagName = $(e.target).text().replace /\s/g, "_"
+      currentTags = @source().val()
+      jumpToEnd = @source()[0].selectionStart == currentTags.length
+
+      if $(e.target).hasClass "highlighted"
+        newVal = currentTags.replace(tagName, "")
+      else
+        newVal = "#{currentTags} #{tagName}"
+
+      newVal = "#{newVal.replace(/^\s+|\s+$/g, "").replace(/\s\s+/g, " ")} "
+      newVal = "" if newVal == " "
+
+      @source().val(newVal)
+      @source()[0].selectionStart = newVal.length if jumpToEnd
+      @highlightList()
+      @source().focus()
+
+    run: (e) ->
+      e.preventDefault()
+
+      tags = @getTags()
+      type = $(e.target).data("type")
+
+      if type == "artist-url"
+        source = @artistSource() || ""
+        return unless source.length > 0 && source.match /^https?:\/\//
+        @fetchStart()
+        $.ajax
+          url: Moebooru.path "/artist.json"
+          data:
+            url: source
+            limit: 10
+          success: $.proxy @fetchArtistSuccess, this
+      else
+        type = null if type == "all"
+        return unless tags.length > 0
+        @fetchStart()
+        $.ajax
+          url: Moebooru.path "/tag/related.json"
+          data: { type: type, tags: tags }
+          success: $.proxy @fetchSuccess, this
+
+    initialize: ->
+      return unless @source().length && @target().length
+      $("[data-toggle='related-tags']").click $.proxy(@run, this)
+      @target().on "click", "a", $.proxy(@toggleTag, this)
+      @source().on "input keyup", $.proxy(@highlightList, this)
+      if @artistSource()
+        $("[data-toggle='related-tags'][data-type='artist-url']").click()
+      else
+        @refreshList()
diff --git a/app/assets/stylesheets/related_tags.css.scss b/app/assets/stylesheets/related_tags.css.scss
new file mode 100644
index 00000000..f9de373e
--- /dev/null
+++ b/app/assets/stylesheets/related_tags.css.scss
@@ -0,0 +1,18 @@
+.tag-column {
+  h6 {
+    font-style: italic;
+  }
+
+  ul {
+    list-style: none;
+
+    li {
+      margin: 0;
+
+      a.highlighted {
+        color: white;
+        background: rgb(0, 111, 250);
+      }
+    }
+  }
+}
diff --git a/app/controllers/tag_controller.rb b/app/controllers/tag_controller.rb
index 133001e4..1255cbff 100644
--- a/app/controllers/tag_controller.rb
+++ b/app/controllers/tag_controller.rb
@@ -123,7 +123,7 @@ class TagController < ApplicationController
   end
 
   def related
-    if params[:type]
+    if params[:type].present?
       @tags = Tag.scan_tags(params[:tags])
       @tags = TagAlias.to_aliased(@tags)
       @tags = @tags.inject({}) do |all, x|
diff --git a/app/views/post/show.html.erb b/app/views/post/show.html.erb
index dab65989..a7b82eea 100644
--- a/app/views/post/show.html.erb
+++ b/app/views/post/show.html.erb
@@ -43,8 +43,6 @@
     <% content_for :post_cookie_javascripts do %>
       <script type="text/javascript">
 
-        RelatedTags.init(Cookie.get('my_tags'), '<%= params[:url] %>')
-
         if (Cookie.get('resize_image') == '1') {
           Post.resize_image()
         }
diff --git a/app/views/post/show_partials/_edit.html.erb b/app/views/post/show_partials/_edit.html.erb
index 1fedeb68..764ffb78 100644
--- a/app/views/post/show_partials/_edit.html.erb
+++ b/app/views/post/show_partials/_edit.html.erb
@@ -62,12 +62,13 @@
             <td>
               <%= text_area "post", "tags", :readonly => !@post.can_be_seen_by?(@current_user), :size => "50x4", :value => @post.cached_tags, :tabindex => 10 %>
             <% if @post.can_be_seen_by?(@current_user) %>
-              <%= link_to_function t('.related.tags'), "RelatedTags.find('post_tags')" %> |
-              <%= link_to_function t('.related.artists'), "RelatedTags.find('post_tags', 'artist')" %> |
-              <%= link_to_function t('.related.characters'), "RelatedTags.find('post_tags', 'char')" %> |
-              <%= link_to_function t('.related.copyrights'), "RelatedTags.find('post_tags', 'copyright')" %>
+              <%= link_to t(".related.tags"), "#", :data => { :toggle => "related-tags", :type => "all" } %> |
+              <%= link_to t(".related.artists"), "#", :data => { :toggle => "related-tags", :type => "artist" } %> |
+              <%= link_to t(".related.characters"), "#", :data => { :toggle => "related-tags", :type => "char" } %> |
+              <%= link_to t(".related.copyrights"), "#", :data => { :toggle => "related-tags", :type => "copyright" } %> |
+              <%= link_to t("post.upload.form.find_related.circles"), "#", :data => { :toggle => "related-tags", :type => "circle" } %>
               <% if CONFIG["enable_artists"] %>
-              | <%= link_to_function(t('.find_artists'), "RelatedTags.find_artist($F('post_source'))") %>
+                | <%= link_to t(".find_artists"), "#", :data => { :toggle => "related-tags", :type => "artist-url" } %>
               <% end %>
             <% end %>
             </td>
diff --git a/app/views/post/upload.html.erb b/app/views/post/upload.html.erb
index caadbdca..93481360 100644
--- a/app/views/post/upload.html.erb
+++ b/app/views/post/upload.html.erb
@@ -79,9 +79,9 @@
               <% end %>
             </th>
             <td>
-              <%= text_field "post", "source", :value => params["url"], :size => 50, :tabindex => 2 %>
+              <%= text_field "post", "source", :value => (params["url"] || params["ref"]), :size => 50, :tabindex => 2 %>
               <% if CONFIG["enable_artists"] %>
-                <%= link_to_function(t('.form.find_artist'), "RelatedTags.find_artist($F('post_source'))") %>
+                <%= link_to t(".form.find_artist"), "#", :data => { :toggle => "related-tags", :type => "artist-url" } %>
               <% end %>
             </td>
           </tr>
@@ -94,11 +94,11 @@
             </th>
             <td>
               <%= text_area "post", "tags", :value => params[:tags], :size => "60x2", :tabindex => 3 %>
-              <%= link_to_function t('.form.find_related.tags'), "RelatedTags.find('post_tags')" %> |
-              <%= link_to_function t('.form.find_related.artists'), "RelatedTags.find('post_tags', 'artist')" %> |
-              <%= link_to_function t('.form.find_related.characters'), "RelatedTags.find('post_tags', 'char')" %> |
-              <%= link_to_function t('.form.find_related.copyrights'), "RelatedTags.find('post_tags', 'copyright')" %> |
-              <%= link_to_function t('.form.find_related.circles'), "RelatedTags.find('post_tags', 'circle')" %>
+              <%= link_to t(".form.find_related.tags"), "#", :data => { :toggle => "related-tags", :type => "all" } %> |
+              <%= link_to t(".form.find_related.artists"), "#", :data => { :toggle => "related-tags", :type => "artist" } %> |
+              <%= link_to t(".form.find_related.characters"), "#", :data => { :toggle => "related-tags", :type => "char" } %> |
+              <%= link_to t(".form.find_related.copyrights"), "#", :data => { :toggle => "related-tags", :type => "copyright" } %> |
+              <%= link_to t(".form.find_related.circles"), "#", :data => { :toggle => "related-tags", :type => "circle" } %>
             </td>
           </tr>
           <% if CONFIG["enable_parent_posts"] %>
@@ -160,12 +160,6 @@
   }.bindAsEventListener());
 </script>
 
-<% content_for :post_cookie_javascripts do %>
-  <script type="text/javascript">
-    RelatedTags.init(Cookie.unescape(Cookie.get('my_tags')), '<%= params[:ref] || params[:url] %>')
-  </script>
-<% end %>
-
 <script type="text/javascript">
   new TagCompletionBox($("post_tags"));
   if(TagCompletion)
diff --git a/lib/assets/javascripts/moe-legacy/related_tags.js b/lib/assets/javascripts/moe-legacy/related_tags.js
deleted file mode 100644
index d8ca59d7..00000000
--- a/lib/assets/javascripts/moe-legacy/related_tags.js
+++ /dev/null
@@ -1,161 +0,0 @@
-RelatedTags = {
-  user_tags: [],
-  recent_tags: [],
-  recent_search: {},
-
-  init: function(user_tags, artist_url) {
-    this.user_tags = (user_tags.match(/\S+/g) || []).sort()
-    this.recent_tags = Cookie.get("recent_tags").match(/\S+/g)
-    if (this.recent_tags) {
-      this.recent_tags = this.recent_tags.sort().uniq(true)
-    } else {
-      this.recent_tags = []
-    }
-
-    if ((artist_url != null) && (artist_url.match(/^http/))) {
-      this.find_artist($F("post_source"))
-    } else {
-      this.build_all({})
-    }
-  },
-
-  toggle: function(link, field) {
-    var field = $(field)
-    var tags = field.value.match(/\S+/g) || []
-    var tag = (link.innerText || link.textContent).replace(/ /g, "_")
-
-    if (tags.include(tag)) {
-      field.value = tags.without(tag).join(" ") + " "
-    } else {
-      field.value = tags.concat([tag]).join(" ") + " "
-    }
-
-    this.build_all(this.recent_search)
-    return false
-  },
-
-  build_html: function(key, tags) {
-    if (tags == null || tags.size() == 0) {
-      return ""
-    }
-
-    var html = ""
-    var current = $F("post_tags").match(/\S+/g) || []
-
-    html += '<div class="tag-column">'
-    html += '<h6><em>' + key.replace(/_/g, " ") + '</em></h6>'
-
-    for (var i=0; i<tags.size(); ++i) {
-      var tag = tags[i]
-      html += ('<a href="/post?tags=' + encodeURIComponent(tag) + '" onclick="RelatedTags.toggle(this, \'post_tags\'); return false"')
-
-      if (current.include(tag)) {
-        html += ' style="background: rgb(0, 111, 250); color: white;"'
-      }
-
-      html += '>' + tag.escapeHTML().replace(/_/g, " ") + '</a><br> '
-    }
-    html += '</div>'
-
-    return html
-  },
-
-  build_all: function(tags) {
-    this.recent_search = tags
-
-    var html = this.build_html("My Tags", this.user_tags) + this.build_html("Recent Tags", this.recent_tags)
-    var keys = []
-
-    for (key in tags) {
-      keys.push(key)
-    }
-
-    keys.sort()
-
-    for (var i=0; i<keys.size(); ++i) {
-      html += this.build_html(keys[i], tags[keys[i]])
-    }
-
-    $("related").update(html)
-  },
-
-  find: function(field, type) {
-    $("related").update("<em>Fetching...</em>")
-    var field = $(field)
-    var tags = null
-    // .textLength is empty in IE9.
-    if (field.textLength == null) {
-      field.textLength = jQuery(field).val().length;
-    };
-
-    // Fetch all related tags if cursor position is either at the beginning or
-    // the end of text area.
-    if ((field.selectionStart == 0) || (field.selectionStart == field.textLength)) {
-      tags = field.value
-    } else {
-      var a = field.selectionStart
-      var b = field.selectionEnd
-
-      if(a != b) {
-        while ((b > 0) && field.value[b] != " ") {
-          b -= 1
-        }
-      }
-      while ((a > 0) && field.value[a] != " ") {
-        a -= 1
-      }
-
-      if (field.value[a] == " ") {
-        a += 1
-      }
-
-      while ((b < field.textLength) && field.value[b] != " ") {
-        b += 1
-      }
-
-      tags = field.value.slice(a, b)
-    }
-
-    var params = {"tags": tags}
-    if (type) {
-      params["type"] = type
-    }
-
-    new Ajax.Request("/tag/related.json", {
-      method: 'get',
-      parameters: params,
-      onComplete: function(resp) {
-        var resp = resp.responseJSON
-        var converted = this.convert_related_js_response(resp)
-        this.build_all(converted)
-      }.bind(this)
-    })
-  },
-
-  convert_related_js_response: function(resp) {
-    var converted = {}
-
-    for (k in resp) {
-      var tags = resp[k].map(function(x) {return x[0]}).sort()
-      converted[k] = tags
-    }
-
-    return converted
-  },
-
-  find_artist: function(url) {
-    if (url.match(/^http/)) {
-      new Ajax.Request("/artist.json", {
-        method: "get",
-        parameters: {
-          "url": url,
-          "limit": "10"
-        },
-        onComplete: function(resp) {
-          var resp = resp.responseJSON
-          this.build_all({"Artist": resp.map(function(x) {return x.name})})
-        }.bind(this)
-      })
-    }
-  }
-}