diff --git a/src/background.ts b/src/background.ts
new file mode 100644
index 0000000..699109d
--- /dev/null
+++ b/src/background.ts
@@ -0,0 +1,194 @@
+import actionApi from './common/actionApi';
+import {isoLangs} from './common/consts';
+import Options from './common/options';
+import ExtSessionStorage from './common/sessionStorage';
+
+interface ContextMenuLangs {
+  [id: string]: string;
+}
+
+function getTranslationUrl(lang: string, text: string): string {
+  let params = new URLSearchParams({
+    sl: 'auto',
+    tl: lang,
+    text: text,
+    op: 'translate',
+  });
+  return 'https://translate.google.com/?' + params.toString();
+}
+
+function translationClick(
+    info: chrome.contextMenus.OnClickData, tab: chrome.tabs.Tab): void {
+  let optionsPromise = Options.getOptions();
+  let ssPromise = ExtSessionStorage.get(['contextMenuLangs', 'translatorTab']);
+  Promise.all([optionsPromise, ssPromise])
+      .then(returnValues => {
+        const [options, sessionStorageItems] = returnValues;
+        let url = getTranslationUrl(
+            sessionStorageItems.contextMenuLangs?.[info.menuItemId],
+            info.selectionText);
+        let settings_tab = {url};
+        if (sessionStorageItems.translatorTab && options.uniqueTab == 'yep') {
+          chrome.tabs.update(
+              sessionStorageItems.translatorTab, settings_tab, tab => {
+                chrome.tabs.highlight(
+                    {
+                      windowId: tab.windowId,
+                      tabs: tab.index,
+                    },
+                    () => {
+                      chrome.windows.update(tab.windowId, {
+                        focused: true,
+                      });
+                    });
+              });
+        } else if (options.uniqueTab == 'popup') {
+          chrome.windows.create({
+            type: 'popup',
+            url,
+            width: 1000,
+            height: 382,
+          });
+        } else {
+          chrome.tabs.create(settings_tab, function(tab) {
+            ExtSessionStorage.set({translatorTab: tab.id});
+          });
+        }
+      })
+      .catch(err => {
+        console.error('Error handling translation click', err);
+      });
+}
+
+function createMenus(options: Options): Promise<void> {
+  chrome.contextMenus.removeAll();
+
+  let contextMenuLangs: ContextMenuLangs = {};
+  let langs = options.targetLangs;
+  let isSingleEntry = Object.values(langs).length == 1;
+
+  let parentEl;
+  if (!isSingleEntry) {
+    parentEl = chrome.contextMenus.create({
+      'id': 'parent',
+      'title': chrome.i18n.getMessage('contextmenu_title'),
+      'contexts': ['selection']
+    });
+  }
+
+  for (let [index, language] of Object.entries(langs)) {
+    let languageDetails = isoLangs[language];
+    if (languageDetails === undefined) {
+      console.error(language + ' doesn\'t exist!');
+      continue;
+    }
+    let title;
+    if (isSingleEntry) {
+      title =
+          chrome.i18n.getMessage('contextmenu_title2', languageDetails.name);
+    } else {
+      title = languageDetails.name + ' (' + languageDetails.nativeName + ')';
+    }
+    let id = chrome.contextMenus.create({
+      'id': 'tr_language_' + language,
+      'title': title,
+      'parentId': parentEl,
+      'contexts': ['selection']
+    });
+    contextMenuLangs[id] = language;
+  }
+
+  if (!isSingleEntry) {
+    chrome.contextMenus.create({
+      'id': 'tr_separator',
+      'type': 'separator',
+      'parentId': parentEl,
+      'contexts': ['selection']
+    });
+    chrome.contextMenus.create({
+      'id': 'tr_options',
+      'title': chrome.i18n.getMessage('contextmenu_edit'),
+      'parentId': parentEl,
+      'contexts': ['selection']
+    });
+  }
+
+  return ExtSessionStorage.set({contextMenuLangs});
+}
+
+chrome.storage.onChanged.addListener((changes, areaName) => {
+  if (areaName == 'sync') {
+    Options.getOptions(/* readOnly = */ false)
+        .then(options => {
+          return createMenus(options);
+        })
+        .catch(err => {
+          console.error(
+              'Error setting up the extension after a change ' +
+                  'in the storage area.',
+              err);
+        });
+  }
+});
+
+Options.getOptions(/* readOnly = */ false)
+    .then(options => {
+      if (options.isFirstRun) {
+        chrome.notifications.create('install', {
+          type: 'basic',
+          iconUrl: 'icons/translate-128.png',
+          title: chrome.i18n.getMessage('notification_install_title'),
+          message: chrome.i18n.getMessage('notification_install_message'),
+          isClickable: true
+        });
+      }
+
+      return createMenus(options);
+    })
+    .catch(err => {
+      console.error('Error initializing the extension.', err);
+    });
+
+chrome.notifications.onClicked.addListener(notification_id => {
+  switch (notification_id) {
+    case 'install':
+      chrome.runtime.openOptionsPage();
+      break;
+  }
+  chrome.notifications.clear(notification_id);
+});
+
+chrome.contextMenus.onClicked.addListener((info, tab) => {
+  if (info.menuItemId == 'tr_options') {
+    chrome.runtime.openOptionsPage();
+  } else {
+    translationClick(info, tab);
+  }
+});
+
+chrome.tabs.onRemoved.addListener((tabId, removeInfo) => {
+  ExtSessionStorage.get('translatorTab')
+      .then(items => {
+        if (tabId == items.translatorTab) {
+          ExtSessionStorage.set({translatorTab: null});
+        }
+      })
+      .catch(err => console.log(err));
+});
+
+actionApi.onClicked.addListener(() => {
+  chrome.runtime.openOptionsPage();
+});
+
+chrome.runtime.onMessage.addListener((request, sender, sendResponse) => {
+  switch (request.action) {
+    case 'clearTranslatorTab':
+      ExtSessionStorage.set({translatorTab: null});
+      break;
+
+    default:
+      console.error(`Unknown action "${request.action}" received as a message.`);
+  }
+
+  return undefined;
+});