diff --git a/beastify/content_scripts/beastify.js b/beastify/content_scripts/beastify.js
index 9b6c5f5..5204ddf 100644
--- a/beastify/content_scripts/beastify.js
+++ b/beastify/content_scripts/beastify.js
@@ -1,18 +1,33 @@
-// Assign beastify() as a listener for messages from the extension.
+/*
+Assign beastify() as a listener for messages from the extension.
+*/
 chrome.runtime.onMessage.addListener(beastify);
 
+/*
+beastify():
+* removes every node in the document.body,
+* then inserts the chosen beast
+* then removes itself as a listener 
+*/
 function beastify(request, sender, sendResponse) {
   removeEverything();
   insertBeast(beastNameToURL(request.beast));
   chrome.runtime.onMessage.removeListener(beastify);
 }
 
+/*
+Remove every node under document.body
+*/
 function removeEverything() {
   while (document.body.firstChild) {
     document.body.firstChild.remove();
   }
 }
 
+/*
+Given a URL to a beast image, create and style an IMG node pointing to
+that image, then insert the node into the document.
+*/
 function insertBeast(beastURL) {
   var beastImage = document.createElement("img");
   beastImage.setAttribute("src", beastURL);
@@ -21,6 +36,9 @@ function insertBeast(beastURL) {
   document.body.appendChild(beastImage);
 }
 
+/*
+Given the name of a beast, get the URL to the corresponding image.
+*/
 function beastNameToURL(beastName) {
   switch (beastName) {
     case "Frog":
diff --git a/borderify/borderify.js b/borderify/borderify.js
index 9c3728b..fa08e19 100644
--- a/borderify/borderify.js
+++ b/borderify/borderify.js
@@ -1 +1,4 @@
+/*
+Just draw a border round the document.body.
+*/
 document.body.style.border = "5px solid red";
diff --git a/notify-link-clicks-i18n/background-script.js b/notify-link-clicks-i18n/background-script.js
index 6bd5baa..b9b1aa2 100644
--- a/notify-link-clicks-i18n/background-script.js
+++ b/notify-link-clicks-i18n/background-script.js
@@ -1,5 +1,13 @@
+/*
+Assign `notify()` as a listener to messages from the content script.
+*/
 chrome.runtime.onMessage.addListener(notify);
 
+/*
+Log that we received the message.
+Then display a notification. The notification contains the URL,
+which we read from the message.
+*/
 function notify(message) {
   console.log("background script received message");
   var title = chrome.i18n.getMessage("notificationTitle");
diff --git a/notify-link-clicks-i18n/content-script.js b/notify-link-clicks-i18n/content-script.js
index 1f0fc94..9eb83da 100644
--- a/notify-link-clicks-i18n/content-script.js
+++ b/notify-link-clicks-i18n/content-script.js
@@ -1,5 +1,12 @@
+/*
+Add notifyExtension() as a listener to click events.
+*/
 window.addEventListener("click", notifyExtension);
 
+/*
+If the click was on a link, send a message to the background page.
+The message contains the link's URL.
+*/
 function notifyExtension(e) {
   var target = e.target;
   while ((target.tagName != "A" || !target.href) && target.parentNode) {
diff --git a/notify-link-clicks/background-script.js b/notify-link-clicks/background-script.js
index 6d70b9a..a111929 100644
--- a/notify-link-clicks/background-script.js
+++ b/notify-link-clicks/background-script.js
@@ -1,5 +1,13 @@
+/*
+Assign `notify()` as a listener to messages from the content script.
+*/
 chrome.runtime.onMessage.addListener(notify);
 
+/*
+Log that we received the message.
+Then display a notification. The notification contains the URL,
+which we read from the message.
+*/
 function notify(message) {
   console.log("background script received message");
   chrome.notifications.create({
diff --git a/notify-link-clicks/content-script.js b/notify-link-clicks/content-script.js
index 1f0fc94..9eb83da 100644
--- a/notify-link-clicks/content-script.js
+++ b/notify-link-clicks/content-script.js
@@ -1,5 +1,12 @@
+/*
+Add notifyExtension() as a listener to click events.
+*/
 window.addEventListener("click", notifyExtension);
 
+/*
+If the click was on a link, send a message to the background page.
+The message contains the link's URL.
+*/
 function notifyExtension(e) {
   var target = e.target;
   while ((target.tagName != "A" || !target.href) && target.parentNode) {
diff --git a/open-my-page-button/background.js b/open-my-page-button/background.js
index d2afdff..d627e4a 100644
--- a/open-my-page-button/background.js
+++ b/open-my-page-button/background.js
@@ -1,5 +1,11 @@
+ /*
+ Add openMyPage() as a listener to clicks on the browser action.
+ */
  chrome.browserAction.onClicked.addListener(openMyPage);
  
+ /*
+ Open a new tab, and load "my-page.html" into it.
+ */
  function openMyPage() {
    console.log("injecting");
     chrome.tabs.create({
diff --git a/user-agent-rewriter/background.js b/user-agent-rewriter/background.js
index 8ef8a39..40255f6 100644
--- a/user-agent-rewriter/background.js
+++ b/user-agent-rewriter/background.js
@@ -1,19 +1,37 @@
 "use strict";
 
+/*
+This is the page for which we want to rewrite the User-Agent header.
+*/
 var targetPage = "http://useragentstring.com/*";
 
+/*
+Map browser names to UA strings.
+*/
 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"
 }
 
+/*
+Initialize the UA to Firefox 41.
+*/
 var ua = uaStrings["Firefox 41"];
 
+/*
+Add rewriteUserAgentHeader as a listener to onBeforeSendHeaders,
+only for the target page.
+
+Make it "blocking" so we can modify the headers.
+*/
 chrome.webRequest.onBeforeSendHeaders.addListener(rewriteUserAgentHeader,
                                           {urls: [targetPage]},
                                           ["blocking", "requestHeaders"]);
 
+/*
+Rewrite the User-Agent header to "ua".
+*/
 function rewriteUserAgentHeader(e) {
   for (var header of e.requestHeaders) {
     if (header.name == "User-Agent") {
@@ -23,6 +41,9 @@ function rewriteUserAgentHeader(e) {
   return {requestHeaders: e.requestHeaders};
 }
 
+/*
+Update ua to a new value, mapped from the uaString parameter.
+*/
 function setUaString(uaString) {
   ua = uaStrings[uaString];
 }
diff --git a/user-agent-rewriter/popup/choose_ua.js b/user-agent-rewriter/popup/choose_ua.js
index a8321f7..0a1869b 100644
--- a/user-agent-rewriter/popup/choose_ua.js
+++ b/user-agent-rewriter/popup/choose_ua.js
@@ -1,3 +1,9 @@
+
+/*
+If the user clicks on an element which has the class "ua-choice":
+* fetch the element's textContent: for example, "IE 11"
+* pass it into the background page's setUaString() function
+*/
 document.addEventListener("click", function(e) {
   if (!e.target.classList.contains("ua-choice")) {
     return;