diff --git a/haskellguide.md b/haskellguide.md
index 202b309..51a0071 100644
--- a/haskellguide.md
+++ b/haskellguide.md
@@ -2,6 +2,9 @@
 
 Revision 1.01
 
+* TOC
+{:toc}
+
 <a id="Background"></a>
 ## Background
 
diff --git a/include/mdguide.css b/include/mdguide.css
index f0cde67..43e9e73 100644
--- a/include/mdguide.css
+++ b/include/mdguide.css
@@ -123,3 +123,24 @@ div.markdown-body div.numbered ~ h4::before {
   border-left-color: var(--callout-warning-border-color) !important;
   color: var(--callout-warning-fg-color) !important;
 }
+
+/* Hide the TOC title entry. */
+#markdown-toc {
+  padding-left: 0;
+}
+#markdown-toc > li::marker {
+  content: '';
+}
+#markdown-toc > li > a {
+  display: none;
+}
+
+/* The TOC can be quite long, so shrink it a little. */
+#markdown-toc {
+  font-size: smaller;
+}
+
+/* Only show TOC entries 2 levels deep. */
+#markdown-toc > li > ul > li > ul > li > ul {
+  display: none;
+}
diff --git a/include/mdguide.js b/include/mdguide.js
index d35b28e..7ad1375 100644
--- a/include/mdguide.js
+++ b/include/mdguide.js
@@ -56,3 +56,21 @@ export function styleAlerts(document) {
     container.classList.add(`callout-${callout}`);
   }
 }
+
+/**
+ * If a TOC exists, clean it up a bit to not take so much space.
+ * @param {!Document} document
+ */
+export function tidyToc(document) {
+  const toc = document.getElementById('markdown-toc');
+  if (!toc) {
+    return;
+  }
+
+  const zippy = document.createElement('details');
+  const summary = document.createElement('summary');
+  summary.textContent = 'Table of Contents';
+  zippy.appendChild(summary);
+  toc.replaceWith(zippy);
+  zippy.appendChild(toc);
+}
diff --git a/include/mdguide_main.js b/include/mdguide_main.js
index 94d482d..d418942 100644
--- a/include/mdguide_main.js
+++ b/include/mdguide_main.js
@@ -8,7 +8,7 @@
  * @fileoverview Main entry point for HTML files to support CSP.
  */
 
-import {styleAlerts} from './mdguide.js';
+import {styleAlerts, tidyToc} from './mdguide.js';
 
 /**
  * Initialize the page.
@@ -16,6 +16,7 @@ import {styleAlerts} from './mdguide.js';
 function main() {
   const document = window.document;
   styleAlerts(document);
+  tidyToc(document);
 }
 
 // We're loaded as a module which defers execution until after the DOM is ready.
diff --git a/jsoncguide.md b/jsoncguide.md
index 0bbc0e3..760250e 100644
--- a/jsoncguide.md
+++ b/jsoncguide.md
@@ -2,6 +2,9 @@
 
 Revision 0.9
 
+* TOC
+{:toc}
+
 <a id="Introduction"></a>
 ## Introduction
 
diff --git a/objcguide.md b/objcguide.md
index 9b1563e..23b4a44 100644
--- a/objcguide.md
+++ b/objcguide.md
@@ -19,6 +19,9 @@
 > refresher, please read [Programming with
 > Objective-C](https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/ProgrammingWithObjectiveC/Introduction/Introduction.html).
 
+* TOC
+{:toc}
+
 ## Principles
 
 ### Optimize for the reader, not the writer
diff --git a/xmlguide.md b/xmlguide.md
index e9e1478..470351c 100644
--- a/xmlguide.md
+++ b/xmlguide.md
@@ -3,6 +3,9 @@
 Version 1.0 \
 Copyright Google 2008
 
+* TOC
+{:toc}
+
 ## Introduction
 
 This document provides a set of guidelines for general use when designing new