diff --git a/docs/guides-navigation.md b/docs/guides-navigation.md
index 7859abe3f2..0d73928c57 100644
--- a/docs/guides-navigation.md
+++ b/docs/guides-navigation.md
@@ -94,6 +94,29 @@ You should provide `directory/id` instead of `id` in `sidebars.json`.
 }
 ```
 
+### Adding Sub Categories 
+
+It is possibile to add sub categories to a sidebar. Instead of passing an array to the category like the previous examples you can pass an object where 
+the keys will be the sub category name. You can then pass an array of document ids to the sub category.
+
+```js
+{
+  "examples-sidebar" : {
+    "My Example Category" : {
+      "My Example Sub Category" : [
+        "my-examples",
+        ...
+      ],
+      "My Next Sub Category" : [
+        "some-other-examples"
+      ]
+      ...
+    },
+    ...
+  }
+}
+```
+
 ### Adding New Sidebars
 
 You can also put a document in a new sidebar. In the following example, we are creating an `examples-sidebar` sidebar within `sidebars.json` that has a category called `My Example Category` containing a document with an `id` of `my-examples`.
diff --git a/lib/core/DocsSidebar.js b/lib/core/DocsSidebar.js
index 87f1ce13ec..fee51480c5 100644
--- a/lib/core/DocsSidebar.js
+++ b/lib/core/DocsSidebar.js
@@ -6,14 +6,30 @@
  */
 
 const React = require('react');
+const fs = require('fs');
 const Container = require('./Container.js');
 const SideNav = require('./nav/SideNav.js');
+const Metadata = require('../core/metadata.js');
 const readCategories = require('../server/readCategories.js');
 
+let languages;
+
+if (fs.existsSync(`../server/languages.js`)) {
+  languages = require(`../server/languages.js`);
+} else {
+  languages = [
+    {
+      enabled: true,
+      name: 'English',
+      tag: 'en',
+    },
+  ];
+}
+
 class DocsSidebar extends React.Component {
   render() {
     const sidebar = this.props.metadata.sidebar;
-    const docsCategories = readCategories(sidebar);
+    const docsCategories = readCategories(sidebar, Metadata, languages);
     const categoryName = docsCategories[this.props.metadata.language][0].name;
     if (!categoryName) {
       return null;
diff --git a/lib/core/nav/SideNav.js b/lib/core/nav/SideNav.js
index 57682c9618..ccd4fdc8d8 100644
--- a/lib/core/nav/SideNav.js
+++ b/lib/core/nav/SideNav.js
@@ -65,7 +65,22 @@ class SideNav extends React.Component {
         <h3 className="navGroupCategoryTitle">
           {this.getLocalizedCategoryString(category.name)}
         </h3>
-        <ul>{category.links.map(this.renderItemLink, this)}</ul>
+        <ul>
+          {category.links.map(this.renderItemLink, this)}
+          {category.sub_categories &&
+            category.sub_categories.map(this.renderSubCategory, this)}
+        </ul>
+      </div>
+    );
+  }
+
+  renderSubCategory(subCategory) {
+    return (
+      <div className="navGroup subNavGroup" key={subCategory.name}>
+        <h4 className="navGroupSubCategoryTitle">
+          {this.getLocalizedCategoryString(subCategory.name)}
+        </h4>
+        <ul>{subCategory.links.map(this.renderItemLink, this)}</ul>
       </div>
     );
   }
diff --git a/lib/server/__tests__/__fixtures__/metadata-subcategories.js b/lib/server/__tests__/__fixtures__/metadata-subcategories.js
new file mode 100644
index 0000000000..005ff534d2
--- /dev/null
+++ b/lib/server/__tests__/__fixtures__/metadata-subcategories.js
@@ -0,0 +1,65 @@
+module.exports = {
+  'en-doc1': {
+    id: 'en-doc1',
+    title: 'Document 1',
+    source: 'doc1.md',
+    version: 'next',
+    permalink: 'docs/en/next/doc1.html',
+    localized_id: 'doc1',
+    language: 'en',
+    sidebar: 'docs',
+    category: 'Test',
+    next_id: 'doc2',
+    next: 'en-doc2',
+    next_title: 'Document 2',
+    sub_category: 'Sub Cat 1',
+    sort: 1,
+  },
+  'en-doc2': {
+    id: 'en-doc2',
+    title: 'Document 2',
+    source: 'doc2.md',
+    version: 'next',
+    permalink: 'docs/en/next/doc2.html',
+    localized_id: 'doc2',
+    language: 'en',
+    sidebar: 'docs',
+    category: 'Test',
+    previous_id: 'doc1',
+    previous: 'en-doc1',
+    previous_title: 'Document 1',
+    sub_category: 'Sub Cat 1',
+    sort: 2,
+  },
+  'en-doc3': {
+    id: 'en-doc3',
+    title: 'Document 3',
+    source: 'doc3.md',
+    version: 'next',
+    permalink: 'docs/en/next/doc3.html',
+    localized_id: 'doc3',
+    language: 'en',
+    sidebar: 'docs',
+    category: 'Test',
+    previous_id: 'doc2',
+    previous: 'en-doc2',
+    previous_title: 'Document 2',
+    sub_category: 'Sub Cat 2',
+    sort: 3,
+  },
+  'en-doc4': {
+    id: 'en-doc4',
+    title: 'Document 4',
+    source: 'doc4.md',
+    version: 'next',
+    permalink: 'docs/en/next/doc4.html',
+    localized_id: 'doc4',
+    language: 'en',
+    sidebar: 'docs',
+    category: 'Test 2',
+    previous_id: 'doc3',
+    previous: 'en-doc3',
+    previous_title: 'Document 3',
+    sort: 4,
+  },
+};
diff --git a/lib/server/__tests__/__fixtures__/metadata.js b/lib/server/__tests__/__fixtures__/metadata.js
index bf4ca08f3e..8ca4afeaf0 100644
--- a/lib/server/__tests__/__fixtures__/metadata.js
+++ b/lib/server/__tests__/__fixtures__/metadata.js
@@ -12,6 +12,7 @@ module.exports = {
     next_id: 'doc2',
     next: 'en-doc2',
     next_title: 'Document 2',
+    sort: 1,
   },
   'en-doc2': {
     id: 'en-doc2',
@@ -26,6 +27,22 @@ module.exports = {
     previous_id: 'doc1',
     previous: 'en-doc1',
     previous_title: 'Document 1',
+    sort: 2,
+  },
+  'en-doc3': {
+    id: 'en-doc3',
+    title: 'Document 3',
+    source: 'doc3.md',
+    version: 'next',
+    permalink: 'docs/en/next/doc3.html',
+    localized_id: 'doc3',
+    language: 'en',
+    sidebar: 'docs',
+    category: 'Test 2',
+    previous_id: 'doc2',
+    previous: 'en-doc2',
+    previous_title: 'Document 2',
+    sort: 3,
   },
   'ko-doc1': {
     id: 'ko-doc1',
diff --git a/lib/server/__tests__/__fixtures__/sidebar-subcategories.js b/lib/server/__tests__/__fixtures__/sidebar-subcategories.js
new file mode 100644
index 0000000000..3af6e72ada
--- /dev/null
+++ b/lib/server/__tests__/__fixtures__/sidebar-subcategories.js
@@ -0,0 +1,11 @@
+module.exports = {
+  docs: {
+    'First Category': {
+      'Sub Cat One': ['doc2', 'doc1'],
+      'Sub Cat Two': ['doc3', 'doc5'],
+    },
+    'Second Category': {
+      Hello: ['doc4'],
+    },
+  },
+};
diff --git a/lib/server/__tests__/__fixtures__/sidebar.js b/lib/server/__tests__/__fixtures__/sidebar.js
new file mode 100644
index 0000000000..8da95c2676
--- /dev/null
+++ b/lib/server/__tests__/__fixtures__/sidebar.js
@@ -0,0 +1,6 @@
+module.exports = {
+  docs: {
+    'First Category': ['doc1', 'doc2'],
+    'Second Category': ['doc4', 'doc3'],
+  },
+};
diff --git a/lib/server/__tests__/readCategories.test.js b/lib/server/__tests__/readCategories.test.js
new file mode 100644
index 0000000000..a2add3c680
--- /dev/null
+++ b/lib/server/__tests__/readCategories.test.js
@@ -0,0 +1,91 @@
+/**
+ * Copyright (c) 2017-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+const readCategories = require('../readCategories');
+const generalMetadata = require('./__fixtures__/metadata.js');
+const subCategoryMetadata = require('./__fixtures__/metadata-subcategories.js');
+
+const languages = [
+  {
+    enabled: true,
+    name: 'English',
+    tag: 'en',
+  },
+  {
+    enabled: true,
+    name: 'Foo',
+    tag: 'ko',
+  },
+];
+
+const languagesMultiple = [
+  {
+    enabled: false,
+    name: 'English',
+    tag: 'en',
+  },
+  {
+    enabled: true,
+    name: 'Foo',
+    tag: 'ko',
+  },
+];
+
+describe('readCategories', () => {
+  test('should return proper categories and their pages', () => {
+    const categories = readCategories('docs', generalMetadata, languages);
+
+    expect(categories.en).toBeDefined();
+    expect(categories.en.length).toBe(2);
+
+    expect(categories.en[0].name).toBe('Test');
+    expect(categories.en[0].links.length).toBe(2);
+    expect(categories.en[0].links[0].id).toBe('en-doc1');
+    expect(categories.en[0].links[1].id).toBe('en-doc2');
+
+    expect(categories.en[1].name).toBe('Test 2');
+    expect(categories.en[1].links.length).toBe(1);
+    expect(categories.en[1].links[0].id).toBe('en-doc3');
+  });
+
+  test('should return proper data with categories and sub categories', () => {
+    const categories = readCategories('docs', subCategoryMetadata, languages);
+
+    expect(categories.en).toBeDefined();
+    expect(categories.ko).toBeDefined();
+    expect(categories.en.length).toBe(2);
+
+    expect(categories.en[0].name).toBe('Test');
+    expect(categories.en[0].links.length).toBe(0);
+    expect(categories.en[0].sub_categories.length).toBe(2);
+
+    expect(categories.en[0].sub_categories[0].name).toBe('Sub Cat 1');
+    expect(categories.en[0].sub_categories[0].links.length).toBe(2);
+    expect(categories.en[0].sub_categories[0].links[0].id).toBe('en-doc1');
+    expect(categories.en[0].sub_categories[0].links[1].id).toBe('en-doc2');
+
+    expect(categories.en[0].sub_categories[1].name).toBe('Sub Cat 2');
+    expect(categories.en[0].sub_categories[1].links.length).toBe(1);
+    expect(categories.en[0].sub_categories[1].links[0].id).toBe('en-doc3');
+
+    expect(categories.en[1].name).toBe('Test 2');
+    expect(categories.en[1].links.length).toBe(1);
+    expect(categories.en[1].links[0].id).toBe('en-doc4');
+    expect(categories.en[1].sub_categories).not.toBeDefined();
+  });
+
+  test('should return proper languages when not enabled', () => {
+    const categories = readCategories(
+      'docs',
+      generalMetadata,
+      languagesMultiple
+    );
+
+    expect(categories.en).not.toBeDefined();
+    expect(categories.ko).toBeDefined();
+  });
+});
diff --git a/lib/server/__tests__/readMetadata.test.js b/lib/server/__tests__/readMetadata.test.js
new file mode 100644
index 0000000000..0edc3f7087
--- /dev/null
+++ b/lib/server/__tests__/readMetadata.test.js
@@ -0,0 +1,77 @@
+/**
+ * Copyright (c) 2017-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+const {readSidebar} = require('../readMetadata');
+const sidebar = require('./__fixtures__/sidebar');
+const sidebarSubCategories = require('./__fixtures__/sidebar-subcategories');
+
+jest.mock('../env', () => ({
+  translation: {
+    enabled: true,
+    enabledLanguages: () => [
+      {
+        enabled: true,
+        name: 'English',
+        tag: 'en',
+      },
+      {
+        enabled: true,
+        name: '한국어',
+        tag: 'ko',
+      },
+    ],
+  },
+  versioning: {
+    enabled: true,
+    defaultVersion: '1.0.0',
+  },
+}));
+
+jest.mock(`${process.cwd()}/siteConfig.js`, () => true, {virtual: true});
+jest.mock(`${process.cwd()}/sidebar.json`, () => true, {virtual: true});
+
+describe('readMetadata', () => {
+  describe('readSidebar', () => {
+    it('should verify regular category data and verify sort', () => {
+      const order = readSidebar(sidebar);
+
+      // Put in this order to verify sort
+      ['doc1', 'doc2', 'doc4', 'doc3'].forEach((id, index) => {
+        expect(order[id]).toBeDefined();
+        expect(order[id].sort).toBe(index + 1);
+      });
+
+      expect(order.doc1.previous).toBeUndefined();
+      expect(order.doc2.previous).toBe('doc1');
+
+      expect(order.doc1.next).toBe('doc2');
+      expect(order.doc2.next).toBe('doc4');
+
+      expect(order.doc1.sub_category).toBeFalsy();
+    });
+
+    test('should verify sub category data and verify sort', () => {
+      const order = readSidebar(sidebarSubCategories);
+
+      // Put in this order to verify sort
+      ['doc2', 'doc1', 'doc3', 'doc5', 'doc4'].forEach((id, index) => {
+        expect(order[id]).toBeDefined();
+        expect(order[id].sort).toBe(index + 1);
+      });
+
+      expect(order.doc2.sidebar).toBe('docs');
+      expect(order.doc2.category).toBe('First Category');
+      expect(order.doc2.sub_category).toBe('Sub Cat One');
+
+      expect(order.doc1.category).toBe('First Category');
+      expect(order.doc1.sub_category).toBe('Sub Cat One');
+
+      expect(order.doc3.category).toBe('First Category');
+      expect(order.doc3.sub_category).toBe('Sub Cat Two');
+    });
+  });
+});
diff --git a/lib/server/__tests__/utils.test.js b/lib/server/__tests__/utils.test.js
index 78769fbf11..490f69ee15 100644
--- a/lib/server/__tests__/utils.test.js
+++ b/lib/server/__tests__/utils.test.js
@@ -88,4 +88,63 @@ describe('server utils', () => {
     expect(utils.getSubDir(docE, docsDir)).toBeNull();
     expect(utils.getSubDir(docE, translatedDir)).toEqual('lol/lah');
   });
+
+  describe('validateSidebar', () => {
+    test('should throw an error for invalid pages', () => {
+      const metadata = {
+        id: 'doc1',
+        sidebar: 'docs',
+        next_id: 'doc2',
+        next: 'doc2',
+      };
+
+      const pages = {
+        doc1: {},
+      };
+
+      expect(() => {
+        utils.validateSidebar(metadata, pages);
+      }).toThrow(
+        `Improper sidebars.json file, document with id 'doc2' not found. Make sure that documents with the ids specified in sidebars.json exist and that no ids are repeated.`
+      );
+    });
+
+    test('should throw an error for invalid version pages', () => {
+      const metadata = {
+        id: 'doc1',
+        version: 'foo',
+        sidebar: 'docs',
+        next_id: 'doc2',
+        next: 'doc2',
+      };
+
+      const pages = {
+        doc1: {},
+      };
+
+      expect(() => {
+        utils.validateSidebar(metadata, pages);
+      }).toThrow(
+        `Improper sidebars file for version foo, document with id 'doc2' not found. Make sure that all documents with ids specified in this version's sidebar file exist and that no ids are repeated.`
+      );
+    });
+
+    test('should pass validate', () => {
+      const metadata = {
+        id: 'doc1',
+        sidebar: 'docs',
+        next_id: 'doc2',
+        next: 'doc2',
+      };
+
+      const pages = {
+        doc1: {},
+        doc2: {},
+      };
+
+      expect(() => {
+        utils.validateSidebar(metadata, pages);
+      }).not.toThrow();
+    });
+  });
 });
diff --git a/lib/server/readCategories.js b/lib/server/readCategories.js
index 21c22427c5..2a265a0ba3 100644
--- a/lib/server/readCategories.js
+++ b/lib/server/readCategories.js
@@ -5,101 +5,112 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-const fs = require('fs');
-
-const Metadata = require('../core/metadata.js');
-
-const CWD = process.cwd();
-let languages;
-if (fs.existsSync(`${CWD}/languages.js`)) {
-  languages = require(`${CWD}/languages.js`);
-} else {
-  languages = [
-    {
-      enabled: true,
-      name: 'English',
-      tag: 'en',
-    },
-  ];
-}
+const {validateSidebar} = require('./utils');
 
 // returns data broken up into categories for a sidebar
-function readCategories(sidebar) {
+function readCategories(sidebar, allMetadata, languages) {
   const enabledLanguages = languages
     .filter(lang => lang.enabled)
     .map(lang => lang.tag);
 
   const allCategories = {};
 
+  // Go through each language that might be defined
   for (let k = 0; k < enabledLanguages.length; ++k) {
     const language = enabledLanguages[k];
-
     const metadatas = [];
-    Object.keys(Metadata).forEach(id => {
-      const metadata = Metadata[id];
+    const categories = [];
+    const pages = {};
+
+    // Get the metadata for the current sidebar
+    Object.keys(allMetadata).forEach(id => {
+      const metadata = allMetadata[id];
       if (metadata.sidebar === sidebar && metadata.language === language) {
         metadatas.push(metadata);
+        pages[metadata.id] = metadata;
       }
     });
 
-    // Build a hashmap of article_id -> metadata
-    const articles = {};
+    // Sort the metadata
+    metadatas.sort((a, b) => a.sort - b.sort);
+
+    // Store the correct sort of categories and sub categories for later
+    const sortedCategories = [];
+    const sortedSubCategories = [];
     for (let i = 0; i < metadatas.length; ++i) {
       const metadata = metadatas[i];
-      articles[metadata.id] = metadata;
+      const category = metadata.category;
+      const subCategory = metadata.sub_category;
+
+      if (!sortedCategories.includes(category)) {
+        sortedCategories.push(category);
+      }
+
+      if (subCategory && !sortedSubCategories.includes(subCategory)) {
+        sortedSubCategories.push(subCategory);
+      }
     }
 
-    // Build a hashmap of article_id -> previous_id
-    const previous = {};
-    for (let i = 0; i < metadatas.length; ++i) {
+    // Index categories and sub categories with all of their documents
+    const indexedCategories = {};
+    const indexedSubCategories = {};
+    for (let i = 0; i < metadatas.length; i++) {
       const metadata = metadatas[i];
-      if (metadata.next) {
-        if (!articles[metadata.next]) {
-          throw new Error(
-            metadata.version
-              ? `Improper sidebars file for version ${
-                  metadata.version
-                }, document with id '${
-                  metadata.next
-                }' not found. Make sure that all documents with ids specified in this version's sidebar file exist and that no ids are repeated.`
-              : `Improper sidebars.json file, document with id '${
-                  metadata.next
-                }' not found. Make sure that documents with the ids specified in sidebars.json exist and that no ids are repeated.`
-          );
+      const category = metadata.category;
+      const subCategory = metadata.sub_category;
+
+      // Validate pages in the sidebar
+      validateSidebar(metadata, pages);
+
+      if (!indexedCategories[category]) {
+        indexedCategories[category] = [];
+      }
+
+      if (!subCategory) {
+        indexedCategories[category].push(metadata);
+      }
+
+      if (subCategory) {
+        if (!indexedSubCategories[category]) {
+          indexedSubCategories[category] = {};
         }
-        previous[articles[metadata.next].id] = metadata.id;
-      }
-    }
 
-    // Find the first element which doesn't have any previous
-    let first = null;
-    for (let i = 0; i < metadatas.length; ++i) {
-      const metadata = metadatas[i];
-      if (!previous[metadata.id]) {
-        first = metadata;
-        break;
-      }
-    }
-
-    const categories = [];
-    let currentCategory = null;
-
-    let metadata = first;
-    let i = 0;
-    while (metadata && i++ < 1000) {
-      if (!currentCategory || metadata.category !== currentCategory.name) {
-        if (currentCategory) {
-          categories.push(currentCategory);
+        if (!indexedSubCategories[category][subCategory]) {
+          indexedSubCategories[category][subCategory] = [];
         }
-        currentCategory = {
-          name: metadata.category,
-          links: [],
-        };
+
+        indexedSubCategories[category][subCategory].push(metadata);
       }
-      currentCategory.links.push(metadata);
-      metadata = articles[metadata.next];
     }
-    categories.push(currentCategory);
+
+    // Generate data for each category and sub categories
+    for (let i = 0; i < sortedCategories.length; i++) {
+      const category = sortedCategories[i];
+      const currentCategory = {
+        name: category,
+        links: indexedCategories[category],
+      };
+
+      for (let ii = 0; ii < sortedSubCategories.length; ii++) {
+        const subCategory = sortedSubCategories[ii];
+
+        if (
+          indexedSubCategories[category] &&
+          indexedSubCategories[category][subCategory]
+        ) {
+          if (!currentCategory.sub_categories) {
+            currentCategory.sub_categories = [];
+          }
+
+          currentCategory.sub_categories.push({
+            name: subCategory,
+            links: indexedSubCategories[category][subCategory],
+          });
+        }
+      }
+
+      categories.push(currentCategory);
+    }
 
     allCategories[language] = categories;
   }
diff --git a/lib/server/readMetadata.js b/lib/server/readMetadata.js
index db6060bae2..439f11eeaf 100644
--- a/lib/server/readMetadata.js
+++ b/lib/server/readMetadata.js
@@ -33,6 +33,13 @@ const SupportedHeaderFields = new Set([
   'custom_edit_url',
 ]);
 
+let allSidebars;
+if (fs.existsSync(`${CWD}/sidebars.json`)) {
+  allSidebars = require(`${CWD}/sidebars.json`);
+} else {
+  allSidebars = {};
+}
+
 // Can have a custom docs path. Top level folder still needs to be in directory
 // at the same level as `website`, not inside `website`.
 //   e.g., docs/whereDocsReallyExist
@@ -42,27 +49,36 @@ const SupportedHeaderFields = new Set([
 function getDocsPath() {
   return siteConfig.customDocsPath ? siteConfig.customDocsPath : 'docs';
 }
+
 // returns map from id to object containing sidebar ordering info
-function readSidebar() {
-  let allSidebars;
-  if (fs.existsSync(`${CWD}/sidebars.json`)) {
-    allSidebars = require(`${CWD}/sidebars.json`);
-  } else {
-    allSidebars = {};
-  }
-  Object.assign(allSidebars, versionFallback.sidebarData());
+function readSidebar(sidebars = {}) {
+  Object.assign(sidebars, versionFallback.sidebarData());
 
   const order = {};
 
-  Object.keys(allSidebars).forEach(sidebar => {
-    const categories = allSidebars[sidebar];
+  Object.keys(sidebars).forEach(sidebar => {
+    const categories = sidebars[sidebar];
 
     let ids = [];
     const categoryOrder = [];
+    const subCategoryOrder = [];
     Object.keys(categories).forEach(category => {
-      ids = ids.concat(categories[category]);
-      for (let i = 0; i < categories[category].length; i++) {
-        categoryOrder.push(category);
+      if (Array.isArray(categories[category])) {
+        ids = ids.concat(categories[category]);
+
+        for (let i = 0; i < categories[category].length; i++) {
+          categoryOrder.push(category);
+          subCategoryOrder.push('');
+        }
+      } else {
+        Object.keys(categories[category]).forEach(subCategory => {
+          ids = ids.concat(categories[category][subCategory]);
+
+          for (let i = 0; i < categories[category][subCategory].length; i++) {
+            categoryOrder.push(category);
+            subCategoryOrder.push(subCategory);
+          }
+        });
       }
     });
 
@@ -70,16 +86,22 @@ function readSidebar() {
       const id = ids[i];
       let previous;
       let next;
+
       if (i > 0) previous = ids[i - 1];
+
       if (i < ids.length - 1) next = ids[i + 1];
+
       order[id] = {
         previous,
         next,
         sidebar,
         category: categoryOrder[i],
+        sub_category: subCategoryOrder[i],
+        sort: i + 1,
       };
     }
   });
+
   return order;
 }
 
@@ -139,12 +161,14 @@ function processMetadata(file, refDir) {
   metadata.id = (env.translation.enabled ? `${language}-` : '') + metadata.id;
   metadata.language = env.translation.enabled ? language : 'en';
 
-  const order = readSidebar();
+  const order = readSidebar(allSidebars);
   const id = metadata.localized_id;
 
   if (order[id]) {
     metadata.sidebar = order[id].sidebar;
     metadata.category = order[id].category;
+    metadata.sub_category = order[id].sub_category;
+    metadata.sort = order[id].sort;
 
     if (order[id].next) {
       metadata.next_id = order[id].next;
@@ -165,7 +189,7 @@ function processMetadata(file, refDir) {
 function generateMetadataDocs() {
   let order;
   try {
-    order = readSidebar();
+    order = readSidebar(allSidebars);
   } catch (e) {
     console.error(e);
     process.exit(1);
@@ -248,6 +272,9 @@ function generateMetadataDocs() {
     if (order[id]) {
       metadata.sidebar = order[id].sidebar;
       metadata.category = order[id].category;
+      metadata.sub_category = order[id].sub_category;
+      metadata.sort = order[id].sort;
+
       if (order[id].next) {
         metadata.next_id = order[id].next.replace(
           `version-${metadata.version}-`,
diff --git a/lib/server/utils.js b/lib/server/utils.js
index d93c71265b..dcad401ca4 100644
--- a/lib/server/utils.js
+++ b/lib/server/utils.js
@@ -64,10 +64,30 @@ function autoPrefixCss(cssContent) {
     .then(result => result.css);
 }
 
+// Validate the docs in the sidebar are valid
+function validateSidebar(metadata, pages) {
+  if (metadata.next) {
+    if (!pages[metadata.next]) {
+      throw new Error(
+        metadata.version
+          ? `Improper sidebars file for version ${
+              metadata.version
+            }, document with id '${
+              metadata.next
+            }' not found. Make sure that all documents with ids specified in this version's sidebar file exist and that no ids are repeated.`
+          : `Improper sidebars.json file, document with id '${
+              metadata.next
+            }' not found. Make sure that documents with the ids specified in sidebars.json exist and that no ids are repeated.`
+      );
+    }
+  }
+}
+
 module.exports = {
   getSubDir,
   getLanguage,
   isSeparateCss,
   minifyCss,
   autoPrefixCss,
+  validateSidebar,
 };
diff --git a/lib/static/css/main.css b/lib/static/css/main.css
index 322673ebd2..eb88a413be 100644
--- a/lib/static/css/main.css
+++ b/lib/static/css/main.css
@@ -1718,7 +1718,12 @@ input::placeholder {
   margin-bottom: 16px;
 }
 
-.toc .toggleNav .navGroup .navGroupCategoryTitle {
+.toc .toggleNav .subNavGroup {
+  margin-top : 16px;
+}
+
+.toc .toggleNav .navGroup .navGroupCategoryTitle,
+.toc .toggleNav .navGroup .navGroupSubCategoryTitle {
   color: #393939;
   font-size: 18px;
   font-weight: 500;
@@ -1727,6 +1732,10 @@ input::placeholder {
   margin-top: 0;
 }
 
+.toc .toggleNav .navGroup .navGroupSubCategoryTitle {
+  font-size: 16px;
+}
+
 .toc .toggleNav .navGroup .navListItem {
   margin: 0;
 }