Example extensions

To illustrate how to use the WebExtension APIs, we maintain a repository of example extensions at https://github.com/mdn/webextensions-examples. This article describes how to run these examples and lists the examples along with the WebExtension APIs they demonstrate.

These examples work in Firefox Nightly: most work in earlier versions of Firefox, but check the strict_min_version key in the extension's manifest.json to make sure.

To try these examples, clone the repository, then install and run the extension using one of these options:

• use the Load Temporary Add-on feature and open the extension from its source folder.
• install web-ext, open the extension's source folder at the command line, and use web-ext run.

The extension stays loaded until you restart Firefox.

If you want to contribute to the repository, send us a pull request.

Name	Description	JavaScript APIs
annotate-page	Displays a sidebar that lets you take notes on web pages.	storage.local tabs.onActivated tabs.onUpdated tabs.query tabs.Tab windows.getCurrent windows.Window
apply-css	Adds a page action to the toolbar. Click the button to apply a red border using injected CSS. Click the button again to remove the CSS.	pageAction.getTitle pageAction.onClicked pageAction.setIcon pageAction.setTitle pageAction.show tabs.insertCSS tabs.onUpdated tabs.query tabs.removeCSS tabs.Tab
beastify	Adds a browser action icon to the toolbar. Click the button to choose a beast. The active tab's body content is then replaced with a picture of the chosen beast.	extension.getURL runtime.onMessage tabs.executeScript tabs.insertCSS tabs.query tabs.removeCSS tabs.sendMessage tabs.Tab
bookmark-it	Adds a bookmark button to the toolbar. Click the button to toggle a bookmark for the current page.	bookmarks.create bookmarks.onCreated bookmarks.onRemoved bookmarks.remove bookmarks.search browserAction.onClicked browserAction.setIcon browserAction.setTitle tabs.onActivated tabs.onUpdated tabs.query tabs.Tab windows.onFocusChanged
borderify	Adds a solid red border to all webpages matching mozilla.org.
chill-out	Show a page action after a period of inactivity. Show cat gifs when the page action is clicked.	alarms.clearAll alarms.create alarms.onAlarm pageAction.hide pageAction.onClicked pageAction.show tabs.get tabs.onActivated tabs.onUpdated tabs.query tabs.update
commands	Demonstrates using the commands API to set up a keyboard shortcut. The shortcut created is accessed using Ctrl+Shift+U (Command+Shift+U on a Mac).	commands.getAll commands.onCommand commands.reset commands.update tabs.create
content-script-register	Illustrates how an extension can register URL-matching content scripts at runtime.	contentScripts.register runtime.onMessage runtime.sendMessage
context-menu-copy-link-with-types	Add a context menu option to links to copy the link to the clipboard, as plain text and as a link in rich HTML.	contextMenus.create contextMenus.onClicked tabs.executeScript
contextual-identities	List, create, and remove contextual identities.	contextualIdentities.query tabs.create tabs.query tabs.remove
cookie-bg-picker	Allows the user to customize the background color and tiled pattern on sites they visit, and also saves their preferences via a cookie, reapplying them whenever they revisit a site they previously customized.	cookies.get cookies.onChanged cookies.remove cookies.set extension.getURL runtime.onMessage tabs.onActivated tabs.onUpdated tabs.query tabs.Tab tabs.sendMessage
devtools-panels	Demonstrates some of the devtools APIs.	devtools.inspectedWindow devtools.panels runtime.getURL runtime.onMessage runtime.sendMessage tabs.executeScript
discogs-search	Demonstrates adding a custom search engine with the chrome_settings_overrides key.
dnr-block-only	Demonstrates how to block network requests without host permissions using the declarativeNetRequest API with the `declarative_net_request` manifest key.	declarativeNetRequest.Rule declarativeNetRequest.RuleAction declarativeNetRequest.RuleCondition
dnr-dynamic-with-options	Demonstrates a generic way to request host permissions and register declarativeNetRequest rules to modify network requests, without any install-time permission warnings. The options_ui page offers a way to request permissions and register DNR rules.	declarativeNetRequest.Rule declarativeNetRequest.getDynamicRules declarativeNetRequest.getSessionRules declarativeNetRequest.updateDynamicRules declarativeNetRequest.updateSessionRules permissions.getAll permissions.remove permissions.request
dnr-redirect-url	Demonstrates multiple ways to redirect requests using the declarativeNetRequest API through the `declarative_net_request` manifest key. Demonstrates aspects of Manifest Version 3 (MV3): action, host_permissions, and web_accessible_resources, and includes a comparison with Manifest Version 2 (MV2).	declarativeNetRequest.Redirect declarativeNetRequest.Rule declarativeNetRequest.RuleAction declarativeNetRequest.RuleCondition declarativeNetRequest.URLTransform permissions.contains permissions.remove permissions.request
dynamic-theme	Dynamic theme example	alarms.create alarms.onAlarm theme.update
emoji-substitution	Replaces words with emojis.
eslint-example	Demonstrates how to configure an extension with eslint.
export-helpers	Demonstrates how to use export helpers like cloneInto to share objects with page scripts.	notifications.create runtime.onMessage runtime.sendMessage
favourite-colour	An example options page, letting you store your favourite colour.	browserAction.onClicked runtime.openOptionsPage storage.managed storage.sync
find-across-tabs	Demonstration of the find API.	browserAction.onClicked extension.getBackgroundPage find.find find.highlightResults runtime.getURL runtime.onMessage runtime.sendMessage tabs.create tabs.query tabs.Tab
firefox-code-search	Demonstrates how to use the omnibox API.	omnibox.onInputChanged omnibox.onInputEntered omnibox.setDefaultSuggestion tabs.create tabs.update
forget-it	Demonstrates how to use the browsingData API.	browserAction.onClicked browsingData.remove notifications.create storage.local
google-userinfo	Demonstrates how to use the identity API.	browserAction.onClicked identity.getRedirectURL identity.launchWebAuthFlow notifications.create
history-deleter	History API demo: deletes history items for a given domain	history.deleteUrl history.search pageAction.show tabs.onUpdated tabs.query
http-response	Demonstrates how to rewrite HTTP responses using the webRequest.filterResponseData() API.	webRequest.filterResponseData webRequest.onBeforeRequest
imagify	Using a sidebar, illustrates the use of file picker and drag and drop. A content script replaces the current page content with the chosen image.	extension.getURL runtime.onMessage tabs.executeScript tabs.query tabs.sendMessage
latest-download	Shows the last downloaded item, and lets you open or delete it.	downloads.erase downloads.getFileIcon downloads.open downloads.removeFile downloads.search
list-cookies	This extensions list the cookies in the active tab.	cookies.getAll tabs.query
menu-accesskey-visible	Shows how to set up a single letter access key for a menu item.	i18n.getMessage menus.update menus.create menus.onClicked
menu-demo	Demonstrates adding and manipulating menu items using the menus API.	i18n.getMessage menus.create menus.onClicked menus.remove menus.update runtime.lastError tabs.executeScript
menu-labelled-open	Shows how an extension can listen for the display of a menu and then add, remove, or update its menu items.	menus.create menus.onClicked menus.onShown menus.refresh menus.update tabs.update
menu-remove-element	Shows how to detect the page element at the cursor position and remove that element, or a parent element, from the page. This example includes use of the polyfill, illustrating cross-browser extension development.	menus.create menus.onClicked menus.getTargetElement pageAction.openPopup pageAction.show tabs.executeScript
menu-search	Illustrates how to retrieve a list of search engines and issue a search request, using search engine details added to the context menu for selected text.	search.search search.get menus.create menus.onClicked
mocha-client-tests	This example shows two methods of testing an extension: running tests from within the extension, and running tests from the command line using Karma.	runtime.onMessage runtime.sendMessage
native-messaging	Example of native messaging, including a Python application and an extension which exchanges messages with it.	browserAction.onClicked runtime.connectNative
navigation-stats	Demonstration of the webNavigation API, showing basic stats about which pages you've visited.	storage.local webNavigation.onCommitted webNavigation.onCompleted
notify-link-clicks-i18n	Shows a localized notification when the user clicks on links.	extension.getURL i18n.getMessage notifications.create runtime.onMessage runtime.sendMessage
open-my-page-button	Adds a browser action icon to the toolbar. When the browser action is clicked, the add-on opens a page that was packaged with it.	browserAction.onClicked tabs.create
page-to-extension-messaging	Demonstrates how a web page and a content script can exchange messages. Visit https://mdn.github.io/webextensions-examples/content-script-page-script-messaging.html for the demo.
permissions	Demonstrates optional permissions using the permissions API.	browserAction.onClicked permissions.getAll permissions.remove permissions.request runtime.getURL tabs.create
private-browsing-theme	Example dynamic theme: sets a dark theme for private windows.	theme.reset theme.update windows.getAll windows.onCreated
proxy-blocker	Uses the proxy API to block requests to hosts specified on a list.	extension.getURL proxy.onRequest proxy.onError storage.local storage.onChanged
quicknote	Allows the user to make quick notes by clicking a button and entering text into the resulting popup. The notes are saved in storage.	storage.local
root-cert-stats	Shows how to get details about a request's TLS connection.	webRequest.getSecurityInfo
runtime-examples	Demo of various runtime APIs.	browserAction.onClicked notifications.create runtime.getManifest runtime.onInstalled runtime.reload
selection-to-clipboard	Demonstrates how to write to the clipboard from a content script
session-state	Demonstrates how to retrieve extension-defined state from restored tabs.	menus.create menus.onClicked sessions.getTabValue sessions.setTabValue tabs.insertCSS tabs.onCreated tabs.onUpdated tabs.query
store-collected-images	Demonstrates how to use the idb-file-storage library to store and manipulate files in an extension.	browserAction.onClicked contextMenus.create contextMenus.onClicked runtime.onMessage runtime.sendMessage tabs.create windows.create
stored-credentials	Performs basic authentication by supplying stored credentials.	storage.local webRequest.onAuthRequired webRequest.onCompleted webRequest.onErrorOccurred
tabs-tabs-tabs	Demonstrates tab manipulation: opening, closing, moving, zooming tabs.	browserAction.setBadgeBackgroundColor browserAction.setBadgeText tabs.create tabs.duplicate tabs.getZoom tabs.move tabs.onCreated tabs.onMoved tabs.onRemoved tabs.query tabs.reload tabs.remove tabs.setZoom tabs.Tab tabs.update
theme-integrated-sidebar	A sidebar that integrates with the current theme.	theme.getCurrent theme.onUpdated windows.getCurrent
theme-switcher	An example of how to use the management API for themes.	management.getAll management.setEnabled
themes	A collection of themes illustrating: weta_fade: a basic theme employing a single image specified in theme_frame:. weta_fade_chrome: the weta_fade theme implemented with Chrome compatible manifest keys. weta_tiled: a theme using a tiled image. weta_mirror: a theme using multiple images and aligning those images in the header. animated: use of an animated PNG.
top-sites	Demonstration of the topSites API.	topSites.get
user-agent-rewriter	Demonstrates using the webRequest API to rewrite the User-Agent HTTP header.	extension.getBackgroundPage webRequest.onBeforeSendHeaders
user-script-register	Illustrates how an extension can register URL-matching user scripts at runtime.	userScripts.register runtime.onMessage runtime.sendMessage
webpack-modules	Demonstrates how to use webpack to package npm modules in an extension.	runtime.onMessage runtime.sendMessage
window-manipulator	Demonstrates how to manipulate windows: opening, closing, resizing windows.	windows.create windows.getAll windows.getCurrent windows.remove windows.update windows.Window
open-irc-links	Demonstrates the use of protocol handlers.