diff --git a/README.md b/README.md
index a1232db..b95f5c5 100644
--- a/README.md
+++ b/README.md
@@ -5,86 +5,4 @@ Example Firefox add-ons created using the [WebExtensions](https://developer.mozi
* To test out an extension in Firefox, see [Packaging and Installation](https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Packaging_and_installation).
-## beastify ##
-
-**Note that this example does not currently work in Firefox.**
-
-An example to accompany a [walkthrough tutorial on MDN](https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Walkthrough).
-
-The extension includes:
-
-* a browser action with a popup including HTML, CSS, and JS
-* a content script
-* three images, each of a different beast, packaged as web accessible resources
-
-When the user clicks the browser action button, the popup is shown, enabling the user to choose one of three beasts.
-
-When they choose, the extension injects the content script into the current page, and sends the content script a message containing the chosen beast.
-
-When the content script receives this message, it replaces all elements in the current page with the packaged image that corresponds to the chosen beast.
-
-**What it shows**
-
-* how to write a browser action with a popup
-* how to give the popup style and behavior using CSS and JS
-* how to inject a content script programmatically into a tab using tabs.executeScript()
-* how to send a message from the main extension to a content script
-* how to use web accessible resources to enable web pages to load packaged content
-
-## borderify ##
-
-This extension just includes:
-
-* a content script, "borderify.js", that is injected into any pages under "mozilla.org/" or any of its subdomains
-
-The content script draws a border around the document.body.
-
-**What it shows**
-
-* how to inject content scripts declaratively using manifest.json
-
-## notify-link-clicks ##
-
-This extension includes:
-
-* a content script, "content-script.js", that is injected into any pages under "mozilla.org/" or any of its subdomains
-* a background script, "background-script.js",
-
-The content script listens for clicks in the page it's attached to. If a click is on a link, it messages the link's href to the background script.
-
-The background script listens for this message. When it receives one, it displays a notification containing the href.
-
-**What it shows**
-
-* how to inject content scripts declaratively using manifest.json
-* how to send messages from a content script to a background script
-* how to display system notifications using the notifications API
-
-## open-my-page ##
-
-This extension includes:
-
-* a background script, "background.js"
-* a browser action
-* a page "my-page.html"
-
-All it does is: when the user clicks the button, open "my-page.html" in a new tab.
-
-**What it shows**
-
-* how to listen for browser action clicks in a background script
-* how to open a page packaged with your extension
-
-## page-to-extension-messaging ##
-
-This extension includes:
-
-* a content script, which is injected only into: "https://mdn.github.io/webextensions-examples/content-script-page-script-messaging.html"
-
-The content script listens for messages from the same window posted using window.postMessage. When the content script receives such a message, it displays an alert.
-
-To test it out, visit https://mdn.github.io/webextensions-examples/content-script-page-script-messaging.html and press the buttons. One button sends a message from the page script to the content script, the other button sends a message in the other direction.
-
-**What it shows**
-
-* how to send messages between page scripts and content scripts
+* To see details of each extension, what it does and what it demonstrates, see the [WebExtensions Examples page](https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Examples).
diff --git a/user-agent-rewriter/background.js b/user-agent-rewriter/background.js
new file mode 100644
index 0000000..545d35a
--- /dev/null
+++ b/user-agent-rewriter/background.js
@@ -0,0 +1,30 @@
+"use strict";
+
+var targetPage = "http://useragentstring.com/*";
+
+var uaStrings = {
+ "Firefox 41": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:41.0) Gecko/20100101 Firefox/41.0",
+ "Chrome 41": "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36",
+ "IE 11": "Mozilla/5.0 (compatible, MSIE 11, Windows NT 6.3; Trident/7.0; rv:11.0) like Gecko"
+}
+
+var ua = uaStrings["Firefox 41"];
+
+chrome.webRequest.onBeforeSendHeaders.addListener(rewriteUserAgentHeader,
+ {urls: [targetPage]},
+ ["blocking", "requestHeaders"]);
+
+function rewriteUserAgentHeader(e) {
+ for (var header of e.requestHeaders) {
+ if (header.name == "User-Agent") {
+ header.value = ua;
+ }
+ }
+ return {requestHeaders: e.requestHeaders};
+}
+
+chrome.runtime.onMessage.addListener(setUaString);
+
+function setUaString(message) {
+ ua = uaStrings[message.uaString];
+}
diff --git a/user-agent-rewriter/button/LICENSE b/user-agent-rewriter/button/LICENSE
new file mode 100644
index 0000000..5a4c0a5
--- /dev/null
+++ b/user-agent-rewriter/button/LICENSE
@@ -0,0 +1 @@
+The icon “choose_ua.png” is taken from Yummygum’s Iconsweets iconset, and is used under the terms of its license (http://yummygum.com/work/iconsweets).
diff --git a/user-agent-rewriter/button/choose_ua.png b/user-agent-rewriter/button/choose_ua.png
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index 0000000..08b9108
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diff --git a/user-agent-rewriter/manifest.json b/user-agent-rewriter/manifest.json
new file mode 100644
index 0000000..29c54d0
--- /dev/null
+++ b/user-agent-rewriter/manifest.json
@@ -0,0 +1,27 @@
+{
+
+ "manifest_version": 2,
+ "name": "user-agent-rewriter",
+ "version": "1.0",
+
+ "applications": {
+ "gecko": {
+ "id": "user-agent-rewriter@mozilla.org"
+ }
+ },
+
+ "permissions": [
+ "webRequest", "webRequestBlocking", "http://useragentstring.com/*"
+ ],
+
+ "background": {
+ "scripts": ["background.js"]
+ },
+
+ "browser_action": {
+ "default_icon": "button/choose_ua.png",
+ "default_title": "Choose a user agent",
+ "default_popup": "popup/choose_ua.html"
+ }
+
+}
diff --git a/user-agent-rewriter/popup/choose_ua.css b/user-agent-rewriter/popup/choose_ua.css
new file mode 100644
index 0000000..2815fd5
--- /dev/null
+++ b/user-agent-rewriter/popup/choose_ua.css
@@ -0,0 +1,18 @@
+html, body {
+ height: 100px;
+ width: 100px;
+ margin: 0;
+}
+
+.ua-choice {
+ height: 20%;
+ width: 90%;
+ margin: 3% auto;
+ padding: 8% 6% 0 6%;
+ background-color: #E5F2F2;
+ cursor: pointer;
+}
+
+.ua-choice:hover {
+ background-color: #CFF2F2;
+}
diff --git a/user-agent-rewriter/popup/choose_ua.html b/user-agent-rewriter/popup/choose_ua.html
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+++ b/user-agent-rewriter/popup/choose_ua.html
@@ -0,0 +1,18 @@
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