diff --git a/test/doctool/test-doctool-html.js b/test/doctool/test-doctool-html.js
index e3d0d4251dcc7d..dd651a66c1e94f 100644
--- a/test/doctool/test-doctool-html.js
+++ b/test/doctool/test-doctool-html.js
@@ -60,25 +60,25 @@ function toHTML({ input, filename, nodeVersion, versions }) {
 const testData = [
   {
     file: fixtures.path('order_of_end_tags_5873.md'),
-    html: '<h3>Static method: Buffer.from(array) <span> ' +
+    html: '<h4>Static method: Buffer.from(array) <span> ' +
       '<a class="mark" href="#foo_static_method_buffer_from_array" ' +
-      'id="foo_static_method_buffer_from_array">#</a> </span> </h3>' +
+      'id="foo_static_method_buffer_from_array">#</a> </span> </h4>' +
       '<ul><li><code>array</code><a ' +
       'href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/' +
       'Reference/Global_Objects/Array" class="type">&#x3C;Array></a></li></ul>'
   },
   {
     file: fixtures.path('doc_with_yaml.md'),
-    html: '<h1>Sample Markdown with YAML info' +
+    html: '<h2>Sample Markdown with YAML info' +
       '<span><a class="mark" href="#foo_sample_markdown_with_yaml_info" ' +
-      ' id="foo_sample_markdown_with_yaml_info">#</a></span></h1>' +
-      '<section><h2>Foobar<span><a class="mark" href="#foo_foobar" ' +
-      'id="foo_foobar">#</a></span></h2>' +
+      ' id="foo_sample_markdown_with_yaml_info">#</a></span></h2>' +
+      '<section><h3>Foobar<span><a class="mark" href="#foo_foobar" ' +
+      'id="foo_foobar">#</a></span></h3>' +
       '<div class="api_metadata"><span>Added in: v1.0.0</span></div> ' +
       '<p>Describe <code>Foobar</code> in more detail here.</p>' +
       '</section><section>' +
-      '<h2>Foobar II<span><a class="mark" href="#foo_foobar_ii" ' +
-      'id="foo_foobar_ii">#</a></span></h2><div class="api_metadata">' +
+      '<h3>Foobar II<span><a class="mark" href="#foo_foobar_ii" ' +
+      'id="foo_foobar_ii">#</a></span></h3><div class="api_metadata">' +
       '<details class="changelog"><summary>History</summary>' +
       '<table><tbody><tr><th>Version</th><th>Changes</th></tr>' +
       '<tr><td>v5.3.0, v4.2.0</td>' +
@@ -88,15 +88,15 @@ const testData = [
       '<p>Describe <code>Foobar II</code> in more detail here.' +
       '<a href="http://man7.org/linux/man-pages/man1/fg.1.html"><code>fg(1)' +
       '</code></a></p></section><section>' +
-      '<h2>Deprecated thingy<span><a class="mark" ' +
+      '<h3>Deprecated thingy<span><a class="mark" ' +
       'href="#foo_deprecated_thingy" id="foo_deprecated_thingy">#</a>' +
-      '</span></h2><div class="api_metadata"><span>Added in: v1.0.0</span>' +
+      '</span></h3><div class="api_metadata"><span>Added in: v1.0.0</span>' +
       '<span>Deprecated since: v2.0.0</span></div><p>Describe ' +
       '<code>Deprecated thingy</code> in more detail here.' +
       '<a href="http://man7.org/linux/man-pages/man1/fg.1p.html"><code>fg(1p)' +
       '</code></a></p></section><section>' +
-      '<h2>Something<span><a class="mark" href="#foo_something' +
-      '" id="foo_something">#</a></span></h2> ' +
+      '<h3>Something<span><a class="mark" href="#foo_something' +
+      '" id="foo_something">#</a></span></h3> ' +
       '<!-- This is not a metadata comment --> ' +
       '<p>Describe <code>Something</code> in more detail here. </p></section>'
   },
@@ -111,19 +111,19 @@ const testData = [
   },
   {
     file: fixtures.path('document_with_links.md'),
-    html: '<h1>Usage and Example<span><a class="mark"' +
+    html: '<h2>Usage and Example<span><a class="mark"' +
     'href="#foo_usage_and_example" id="foo_usage_and_example">#</a>' +
-    '</span></h1><section><h2>Usage<span><a class="mark" href="#foo_usage"' +
-    'id="foo_usage">#</a></span></h2><p><code>node \\[options\\] index.js' +
+    '</span></h2><section><h3>Usage<span><a class="mark" href="#foo_usage"' +
+    'id="foo_usage">#</a></span></h3><p><code>node \\[options\\] index.js' +
     '</code></p><p>Please see the<a href="cli.html#cli-options">' +
     'Command Line Options</a>document for more information.</p>' +
-    '</section><section><h2>' +
+    '</section><section><h3>' +
     'Example<span><a class="mark" href="#foo_example" id="foo_example">' +
-    '#</a></span></h2><p>An example of a<a href="example.html">' +
+    '#</a></span></h3><p>An example of a<a href="example.html">' +
     'webserver</a>written with Node.js which responds with<code>' +
     '\'Hello, World!\'</code>:</p></section><section>' +
-    '<h2>See also<span><a class="mark"' +
-    'href="#foo_see_also" id="foo_see_also">#</a></span></h2><p>Check' +
+    '<h3>See also<span><a class="mark"' +
+    'href="#foo_see_also" id="foo_see_also">#</a></span></h3><p>Check' +
     'out also<a href="https://nodejs.org/">this guide</a></p></section>'
   },
   {
diff --git a/tools/doc/html.js b/tools/doc/html.js
index 67157ba6b5fb09..9089ce7e443232 100644
--- a/tools/doc/html.js
+++ b/tools/doc/html.js
@@ -66,10 +66,19 @@ const gtocHTML = unified()
 const templatePath = path.join(docPath, 'template.html');
 const template = fs.readFileSync(templatePath, 'utf8');
 
-function wrapSections(content) {
+function processContent(content) {
+  content = content.toString();
+  // Increment header tag levels to avoid multiple h1 tags in a doc.
+  // This means we can't already have an <h6>.
+  if (content.includes('<h6>')) {
+    throw new Error('Cannot increment a level 6 header');
+  }
+  // `++level` to convert the string to a number and increment it.
+  content = content.replace(/(?<=<\/?h)[1-5](?=[^<>]*>)/g, (level) => ++level);
+  // Wrap h3 tags in section tags.
   let firstTime = true;
-  return content.toString()
-    .replace(/<h2/g, (heading) => {
+  return content
+    .replace(/<h3/g, (heading) => {
       if (firstTime) {
         firstTime = false;
         return '<section>' + heading;
@@ -91,7 +100,7 @@ function toHTML({ input, content, filename, nodeVersion, versions }) {
                      .replace('__GTOC__', gtocHTML.replace(
                        `class="nav-${id}"`, `class="nav-${id} active"`))
                      .replace('__EDIT_ON_GITHUB__', editOnGitHub(filename))
-                     .replace('__CONTENT__', wrapSections(content));
+                     .replace('__CONTENT__', processContent(content));
 
   const docCreated = input.match(
     /<!--\s*introduced_in\s*=\s*v([0-9]+)\.([0-9]+)\.[0-9]+\s*-->/);