diff --git a/static/tests/backend/specs/textDiff.js b/static/tests/backend/specs/textDiff.js
new file mode 100644
index 0000000..2643e98
--- /dev/null
+++ b/static/tests/backend/specs/textDiff.js
@@ -0,0 +1,34 @@
+'use strict';
+
+const assert = require('assert').strict;
+const textDiff = require('../../../../textDiff');
+
+describe('textDiff', function () {
+  it('returns empty string when text has not changed', async function () {
+    assert.equal(textDiff('line one\nline two\n', 'line one\nline two\n'), '');
+  });
+
+  it('returns added lines with plus prefix', async function () {
+    assert.equal(textDiff('line one\n', 'line one\nline two\n'), '+line two');
+  });
+
+  it('returns removed lines with minus prefix', async function () {
+    assert.equal(textDiff('line one\nline two\n', 'line one\n'), '-line two');
+  });
+
+  it('returns both removed and added lines for replacement', async function () {
+    assert.equal(
+        textDiff('line one\nline two\n', 'line one\nline three\n'),
+        '-line two\n+line three',
+    );
+  });
+
+  it('falls back to simple add/remove output for large texts', async function () {
+    const before = Array.from({length: 1001}, (_, i) => `before-${i}`).join('\n');
+    const after = Array.from({length: 1001}, (_, i) => `after-${i}`).join('\n');
+    const diff = textDiff(before, after);
+    assert(diff.includes('-before-0'));
+    assert(diff.includes('+after-0'));
+    assert(!diff.includes('-before-999'));
+  });
+});
diff --git a/textDiff.js b/textDiff.js
new file mode 100644
index 0000000..d0dfca4
--- /dev/null
+++ b/textDiff.js
@@ -0,0 +1,60 @@
+'use strict';
+
+const splitLines = (text) => {
+  const normalized = String(text ?? '').replace(/\r\n/g, '\n');
+  if (normalized === '') return [];
+  return normalized.endsWith('\n')
+    ? normalized.slice(0, -1).split('\n')
+    : normalized.split('\n');
+};
+
+const MAX_DIFF_LINES = 1000;
+const MAX_DIFF_CELLS = 500000;
+const MAX_FALLBACK_CHANGES = 400;
+
+module.exports = (beforeText, afterText) => {
+  const before = splitLines(beforeText);
+  const after = splitLines(afterText);
+  if (before.length === after.length &&
+      before.every((line, index) => line === after[index])) return '';
+  if (before.length > MAX_DIFF_LINES ||
+      after.length > MAX_DIFF_LINES ||
+      before.length * after.length > MAX_DIFF_CELLS) {
+    const halfLimit = Math.floor(MAX_FALLBACK_CHANGES / 2);
+    return before.slice(0, halfLimit).map((line) => `-${line}`)
+        .concat(after.slice(0, halfLimit).map((line) => `+${line}`))
+        .join('\n');
+  }
+
+  const lcs = Array.from({length: before.length + 1}, () => Array(after.length + 1).fill(0));
+  for (let beforeIdx = 1; beforeIdx <= before.length; beforeIdx++) {
+    for (let afterIdx = 1; afterIdx <= after.length; afterIdx++) {
+      lcs[beforeIdx][afterIdx] = before[beforeIdx - 1] === after[afterIdx - 1]
+        ? lcs[beforeIdx - 1][afterIdx - 1] + 1
+        : Math.max(lcs[beforeIdx - 1][afterIdx], lcs[beforeIdx][afterIdx - 1]);
+    }
+  }
+
+  const changes = [];
+  let beforeIndex = before.length;
+  let afterIndex = after.length;
+  while (beforeIndex > 0 || afterIndex > 0) {
+    if (beforeIndex > 0 && afterIndex > 0 &&
+        before[beforeIndex - 1] === after[afterIndex - 1]) {
+      beforeIndex--;
+      afterIndex--;
+      continue;
+    }
+    if (afterIndex > 0 &&
+        (beforeIndex === 0 ||
+         lcs[beforeIndex][afterIndex - 1] >= lcs[beforeIndex - 1][afterIndex])) {
+      changes.push(`+${after[afterIndex - 1]}`);
+      afterIndex--;
+      continue;
+    }
+    changes.push(`-${before[beforeIndex - 1]}`);
+    beforeIndex--;
+  }
+
+  return changes.reverse().join('\n');
+};
diff --git a/update.js b/update.js
index 3e58eff..f2d1e3c 100644
--- a/update.js
+++ b/update.js
@@ -7,6 +7,7 @@ const API = require('ep_etherpad-lite/node/db/API');
 const email = require('emailjs');
 const settings = require('ep_etherpad-lite/node/utils/Settings');
 const util = require('util');
+const textDiff = require('./textDiff');
 
 const SMTPClient = email.SMTPClient;
 
@@ -35,7 +36,17 @@ const server = new SMTPClient(emailServer);
 
 const emailFooter = "\nYou can unsubscribe from these emails in the pad's Settings window.\n";
 
-exports.padUpdate = (hookName, _pad) => {
+const getPadText = async (padId) => {
+  try {
+    const {text = ''} = await API.getText(padId);
+    return text;
+  } catch (err) {
+    console.error(err);
+    return null;
+  }
+};
+
+exports.padUpdate = async (hookName, _pad) => {
   if (!pluginSettings) return false;
 
   const pad = _pad.pad;
@@ -44,11 +55,15 @@ exports.padUpdate = (hookName, _pad) => {
 
   if (timers[padId]) return; // an interval already exists so don't create
 
+  const startText = await getPadText(padId);
+  timers[padId] = {
+    interval: setInterval(() => sendUpdates(padId), checkFrequency),
+    startText,
+  };
   console.debug(`Someone started editing ${padId}`);
   notifyBegin(padId);
   console.debug(`Created an interval time check for ${padId}`);
   // if not then create one and write it to the timers object
-  timers[padId] = setInterval(() => sendUpdates(padId), checkFrequency);
 };
 
 const padUrl = (padId) => urlToPads + encodeURIComponent(padId);
@@ -86,8 +101,17 @@ const notifyBegin = async (padId) => {
   }));
 };
 
-const notifyEnd = async (padId) => {
-  // TODO: get the modified contents to include in the email
+const notifyEnd = async (padId, startText = '') => {
+  let diffText = '';
+  if (typeof startText === 'string') {
+    try {
+      const {text = ''} = await API.getText(padId);
+      diffText = textDiff(startText, text);
+    } catch (err) {
+      console.error(err);
+    }
+  }
+  const changesSection = diffText ? `\n${diffText}\n` : '';
 
   const recipients = await db.get(`emailSubscription:${padId}`); // get everyone we need to email
   if (!recipients) return;
@@ -107,7 +131,7 @@ const notifyEnd = async (padId) => {
     let message;
     try {
       message = await util.promisify(server.send.bind(server))({
-        text: `This pad is done being edited:\n  <${padUrl(padId)}>\n${emailFooter}`,
+        text: `This pad is done being edited:\n  <${padUrl(padId)}>${changesSection}${emailFooter}`,
         from: `${fromName} <${fromEmail}>`,
         to: recipient,
         subject: `Someone finished editing ${padId}`,
@@ -130,9 +154,11 @@ const sendUpdates = async (padId) => {
     return;
   }
   console.warn('Interval went stale so deleting it from object and timer');
-  clearInterval(timers[padId]); // remove the interval timer
+  const timer = timers[padId];
+  const startText = timer ? timer.startText : null;
+  if (timer) clearInterval(timer.interval); // remove the interval timer
   delete timers[padId]; // remove the entry from the padId
-  await notifyEnd(padId);
+  await notifyEnd(padId, startText);
   // The status of the users relationship with the pad --
   // IE if it's subscribed to this pad / if it's already on the pad
   // This comes frmo the database