diff --git a/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector.js b/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector.js
new file mode 100644
index 0000000..6c3a713
--- /dev/null
+++ b/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector.js
@@ -0,0 +1,68 @@
+// Copyright (C) 2018 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+(function() {
+  'use strict';
+
+  Polymer({
+    is: 'gr-diff-mode-selector',
+
+    properties: {
+      mode: {
+        type: String,
+        notify: true,
+      },
+
+      /**
+       * If set to true, the user's preference will be updated every time a
+       * button is tapped. Don't set to true if there is no user.
+       */
+      saveOnChange: {
+        type: Boolean,
+        value: false,
+      },
+
+      /** @type {?} */
+      _VIEW_MODES: {
+        type: Object,
+        readOnly: true,
+        value: {
+          SIDE_BY_SIDE: 'SIDE_BY_SIDE',
+          UNIFIED: 'UNIFIED_DIFF',
+        },
+      },
+    },
+
+    /**
+     * Set the mode. If save on change is enabled also update the preference.
+     */
+    setMode(newMode) {
+      if (this.saveOnChange && this.mode && this.mode !== newMode) {
+        this.$.restAPI.savePreferences({diff_view: newMode});
+      }
+      this.mode = newMode;
+    },
+
+    _computeSelectedClass(diffViewMode, buttonViewMode) {
+      return buttonViewMode === diffViewMode ? 'selected' : '';
+    },
+
+    _handleSideBySideTap() {
+      this.setMode(this._VIEW_MODES.SIDE_BY_SIDE);
+    },
+
+    _handleUnifiedTap() {
+      this.setMode(this._VIEW_MODES.UNIFIED);
+    },
+  });
+})();