diff --git a/lib/phoenix_html/tag.ex b/lib/phoenix_html/tag.ex
index 3e3ab73..447538b 100644
--- a/lib/phoenix_html/tag.ex
+++ b/lib/phoenix_html/tag.ex
@@ -8,7 +8,8 @@ defmodule Phoenix.HTML.Tag do
 
   import Phoenix.HTML
 
-  @tag_prefixes [:aria, :data]
+  @special_attributes ["data", "aria", "class"]
+
   @csrf_param "_csrf_token"
   @method_param "_method"
 
@@ -49,7 +50,7 @@ defmodule Phoenix.HTML.Tag do
   def tag(name), do: tag(name, [])
 
   def tag(name, attrs) when is_list(attrs) do
-    {:safe, [?<, to_string(name), build_attrs(attrs), ?>]}
+    {:safe, [?<, to_string(name), build_attrs(attrs) |> Enum.sort() |> tag_attrs(), ?>]}
   end
 
   @doc ~S"""
@@ -87,16 +88,49 @@ defmodule Phoenix.HTML.Tag do
   def content_tag(name, content, attrs) when is_list(attrs) do
     name = to_string(name)
     {:safe, escaped} = html_escape(content)
-    {:safe, [?<, name, build_attrs(attrs), ?>, escaped, ?<, ?/, name, ?>]}
+
+    {:safe,
+     [?<, name, build_attrs(attrs) |> Enum.sort() |> tag_attrs(), ?>, escaped, ?<, ?/, name, ?>]}
+  end
+
+  @doc """
+  Escapes a list of attributes, returning iodata.
+
+  Pay attention that, unlike `tag/2` and `content_tag/2`, this
+  function does not sort the attributes.
+
+      iex> attributes_escape(title: "the title", id: "the id", selected: true)
+      {:safe,
+       [
+         [32, "title", 61, 34, "the title", 34],
+         [32, "id", 61, 34, "the id", 34],
+         [32, "selected"]
+       ]}
+
+  """
+  def attributes_escape(attrs) do
+    {:safe, attrs |> build_attrs() |> Enum.reverse() |> tag_attrs()}
   end
 
   defp build_attrs([]), do: []
   defp build_attrs(attrs), do: build_attrs(attrs, [])
 
-  defp build_attrs([], acc), do: acc |> Enum.sort() |> tag_attrs()
+  defp build_attrs([], acc), do: acc
 
-  defp build_attrs([{k, v} | t], acc) when k in @tag_prefixes and is_list(v) do
-    build_attrs(t, nested_attrs(key_escape(k), v, acc))
+  defp build_attrs([{k, v} | t], acc) when k in @special_attributes do
+    build_attrs([{String.to_atom(k), v} | t], acc)
+  end
+
+  defp build_attrs([{:data, v} | t], acc) when is_list(v) do
+    build_attrs(t, nested_attrs("data", v, acc))
+  end
+
+  defp build_attrs([{:aria, v} | t], acc) when is_list(v) do
+    build_attrs(t, nested_attrs("aria", v, acc))
+  end
+
+  defp build_attrs([{:class, v} | t], acc) when is_list(v) do
+    build_attrs(t, [{"class", class_value(v)} | acc])
   end
 
   defp build_attrs([{k, true} | t], acc) do
@@ -137,6 +171,16 @@ defmodule Phoenix.HTML.Tag do
     end)
   end
 
+  defp class_value(value) when is_list(value) do
+    value
+    |> Enum.filter(& &1)
+    |> Enum.join(" ")
+  end
+
+  defp class_value(value) do
+    value
+  end
+
   defp key_escape(value) when is_atom(value), do: String.replace(Atom.to_string(value), "_", "-")
   defp key_escape(value), do: attr_escape(value)
 
diff --git a/test/phoenix_html/tag_test.exs b/test/phoenix_html/tag_test.exs
index b867b01..bdbd624 100644
--- a/test/phoenix_html/tag_test.exs
+++ b/test/phoenix_html/tag_test.exs
@@ -5,6 +5,61 @@ defmodule Phoenix.HTML.TagTest do
   import Phoenix.HTML.Tag
   doctest Phoenix.HTML.Tag
 
+  describe "attributes_escape" do
+    test "key as atom" do
+      assert attributes_escape([{:title, "the title"}]) |> safe_to_string() ==
+               ~s( title="the title")
+    end
+
+    test "key as string" do
+      assert attributes_escape([{"title", "the title"}]) |> safe_to_string() ==
+               ~s( title="the title")
+    end
+
+    test "convert snake_case keys into kebab-case when key is atom" do
+      assert attributes_escape([{:my_attr, "value"}]) |> safe_to_string() == ~s( my-attr="value")
+    end
+
+    test "keep snake_case keys when key is string" do
+      assert attributes_escape([{"my_attr", "value"}]) |> safe_to_string() == ~s( my_attr="value")
+    end
+
+    test "multiple attributes" do
+      assert attributes_escape([{:title, "the title"}, {:id, "the id"}]) |> safe_to_string() ==
+               ~s( title="the title" id="the id")
+    end
+
+    test "handle nested data" do
+      assert attributes_escape([{"data", [a: "1", b: "2"]}]) |> safe_to_string() ==
+               ~s( data-a="1" data-b="2")
+
+      assert attributes_escape([{"aria", [a: "1", b: "2"]}]) |> safe_to_string() ==
+               ~s( aria-a="1" aria-b="2")
+    end
+
+    test "handle class value as string" do
+      assert attributes_escape([{:class, "btn"}]) |> safe_to_string() == ~s( class="btn")
+    end
+
+    test "handle class value as list" do
+      assert attributes_escape([{:class, ["btn", nil, false, "active"]}]) |> safe_to_string() ==
+               ~s( class="btn active")
+    end
+
+    test "handle class key as string" do
+      assert attributes_escape([{"class", "btn"}]) |> safe_to_string() == ~s( class="btn")
+    end
+
+    test "supress attribute when value is falsy" do
+      assert attributes_escape([{"title", nil}]) |> safe_to_string() == ~s()
+      assert attributes_escape([{"title", false}]) |> safe_to_string() == ~s()
+    end
+
+    test "supress value when value is true" do
+      assert attributes_escape([{"selected", true}]) |> safe_to_string() == ~s( selected)
+    end
+  end
+
   test "tag" do
     assert tag(:br) |> safe_to_string() == ~s(<br>)
 
@@ -20,8 +75,12 @@ defmodule Phoenix.HTML.TagTest do
              ~s(<input data-toggle="dropdown">)
 
     assert tag(:input, my_attr: "blah") |> safe_to_string() == ~s(<input my-attr="blah">)
-    assert tag(:input, [{"my_<_attr", "blah"}]) |> safe_to_string() == ~s(<input my_&lt;_attr="blah">)
-    assert tag(:input, [{{:safe, "my_<_attr"}, "blah"}]) |> safe_to_string() == ~s(<input my_<_attr="blah">)
+
+    assert tag(:input, [{"my_<_attr", "blah"}]) |> safe_to_string() ==
+             ~s(<input my_&lt;_attr="blah">)
+
+    assert tag(:input, [{{:safe, "my_<_attr"}, "blah"}]) |> safe_to_string() ==
+             ~s(<input my_<_attr="blah">)
 
     assert tag(:input, data: [my_attr: "blah"]) |> safe_to_string() ==
              ~s(<input data-my-attr="blah">)