diff --git a/readthedocs/builds/models.py b/readthedocs/builds/models.py
index c36ba7c37cf..ad26a15244c 100644
--- a/readthedocs/builds/models.py
+++ b/readthedocs/builds/models.py
@@ -78,6 +78,8 @@
     MEDIA_TYPES,
     PRIVACY_CHOICES,
     SPHINX,
+    SPHINX_HTMLDIR,
+    SPHINX_SINGLEHTML,
 )
 from readthedocs.projects.models import APIProject, Project
 from readthedocs.projects.version_handling import determine_stable_version
@@ -361,6 +363,10 @@ def supports_wipe(self):
         """Return True if version is not external."""
         return not self.type == EXTERNAL
 
+    @property
+    def is_sphinx_type(self):
+        return self.documentation_type in {SPHINX, SPHINX_HTMLDIR, SPHINX_SINGLEHTML}
+
     def get_subdomain_url(self):
         external = self.type == EXTERNAL
         return self.project.get_docs_url(
diff --git a/readthedocs/doc_builder/backends/mkdocs.py b/readthedocs/doc_builder/backends/mkdocs.py
index 2b0842829d0..2239eb75c15 100644
--- a/readthedocs/doc_builder/backends/mkdocs.py
+++ b/readthedocs/doc_builder/backends/mkdocs.py
@@ -11,10 +11,10 @@
 import yaml
 from django.conf import settings
 from django.template import loader as template_loader
-from readthedocs.projects.constants import MKDOCS_HTML, MKDOCS
 
 from readthedocs.doc_builder.base import BaseBuilder
 from readthedocs.doc_builder.exceptions import MkDocsYAMLParseError
+from readthedocs.projects.constants import MKDOCS, MKDOCS_HTML
 from readthedocs.projects.models import Feature
 
 
@@ -314,17 +314,12 @@ def get_theme_name(self, mkdocs_config):
 
 
 class MkdocsHTML(BaseMkdocs):
+
     type = 'mkdocs'
     builder = 'build'
     build_dir = '_build/html'
 
 
-class MkdocsJSON(BaseMkdocs):
-    type = 'mkdocs_json'
-    builder = 'json'
-    build_dir = '_build/json'
-
-
 class SafeLoaderIgnoreUnknown(yaml.SafeLoader):  # pylint: disable=too-many-ancestors
 
     """
diff --git a/readthedocs/doc_builder/loader.py b/readthedocs/doc_builder/loader.py
index 1f8d8256567..bf826fd17c3 100644
--- a/readthedocs/doc_builder/loader.py
+++ b/readthedocs/doc_builder/loader.py
@@ -1,5 +1,3 @@
-# -*- coding: utf-8 -*-
-
 """Lookup tables for builders and backends."""
 from importlib import import_module
 
@@ -21,7 +19,6 @@
     'sphinx_singlehtmllocalmedia': sphinx.LocalMediaBuilder,
     # Other markup
     'mkdocs': mkdocs.MkdocsHTML,
-    'mkdocs_json': mkdocs.MkdocsJSON,
 }
 
 
diff --git a/readthedocs/projects/models.py b/readthedocs/projects/models.py
index 65af1bc7688..b31d76f69de 100644
--- a/readthedocs/projects/models.py
+++ b/readthedocs/projects/models.py
@@ -39,7 +39,7 @@
     validate_repository_url,
 )
 from readthedocs.projects.version_handling import determine_stable_version
-from readthedocs.search.parse_json import process_file
+from readthedocs.search.parse_json import process_file, process_mkdocs_index_file
 from readthedocs.vcs_support.backends import backend_cls
 from readthedocs.vcs_support.utils import Lock, NonBlockingLock
 
@@ -1329,7 +1329,7 @@ class Meta:
 
     objects = HTMLFileManager.from_queryset(HTMLFileQuerySet)()
 
-    def get_processed_json(self):
+    def get_processed_json_sphinx(self):
         """
         Get the parsed JSON for search indexing.
 
@@ -1373,6 +1373,52 @@ def get_processed_json(self):
             'domain_data': {},
         }
 
+    def get_processed_json_mkdocs(self):
+        log.debug('Processing mkdocs index')
+        storage = get_storage_class(settings.RTD_BUILD_MEDIA_STORAGE)()
+        storage_path = self.project.get_storage_path(
+            type_='html', version_slug=self.version.slug, include_file=False
+        )
+        try:
+            file_path = storage.join(storage_path, 'search/search_index.json')
+            if storage.exists(file_path):
+                index_data = process_mkdocs_index_file(file_path, page=self.path)
+                if index_data:
+                    return index_data
+        except Exception:
+            log.warning(
+                'Unhandled exception during search processing file: %s',
+                file_path,
+            )
+        return {
+            'path': self.path,
+            'title': '',
+            'sections': [],
+            'domain_data': {},
+        }
+
+    def get_processed_json(self):
+        """
+        Get the parsed JSON for search indexing.
+
+        Returns a dictionary with the following structure.
+        {
+            'path': 'file path',
+            'title': 'Title',
+            'sections': [
+                {
+                    'id': 'section-anchor',
+                    'title': 'Section title',
+                    'content': 'Section content',
+                },
+            ],
+            'domain_data': {},
+        }
+        """
+        if self.version.is_sphinx_type:
+            return self.get_processed_json_sphinx()
+        return self.get_processed_json_mkdocs()
+
     @cached_property
     def processed_json(self):
         return self.get_processed_json()
diff --git a/readthedocs/projects/tasks.py b/readthedocs/projects/tasks.py
index 98025185c5a..39afb6d7711 100644
--- a/readthedocs/projects/tasks.py
+++ b/readthedocs/projects/tasks.py
@@ -1234,12 +1234,14 @@ def get_final_doctype(self):
         return html_builder.get_final_doctype()
 
     def build_docs_search(self):
-        """Build search data."""
-        # Search is always run in sphinx using the rtd-sphinx-extension.
-        # Mkdocs has no search currently.
-        if self.is_type_sphinx() and self.version.type != EXTERNAL:
-            return True
-        return False
+        """
+        Build search data.
+
+        .. note::
+           For MkDocs search is indexed from its ``html`` artifacts.
+           And in sphinx is run using the rtd-sphinx-extension.
+        """
+        return self.is_type_sphinx() and self.version.type != EXTERNAL
 
     def build_docs_localmedia(self):
         """Get local media files with separate build."""
@@ -1593,6 +1595,9 @@ def _create_intersphinx_data(version, commit, build):
     :param commit: Commit that updated path
     :param build: Build id
     """
+    if not version.is_sphinx_type:
+        return
+
     storage = get_storage_class(settings.RTD_BUILD_MEDIA_STORAGE)()
 
     html_storage_path = version.project.get_storage_path(
diff --git a/readthedocs/search/documents.py b/readthedocs/search/documents.py
index 9ea3b704f65..68dd80ee8d3 100644
--- a/readthedocs/search/documents.py
+++ b/readthedocs/search/documents.py
@@ -109,8 +109,10 @@ class Meta:
 
     def prepare_domains(self, html_file):
         """Prepares and returns the values for domains field."""
-        all_domains = []
+        if not html_file.version.is_sphinx_type:
+            return []
 
+        all_domains = []
         try:
             domains_qs = html_file.sphinx_domains.exclude(
                 domain='std',
@@ -172,11 +174,8 @@ def get_queryset(self):
         """Overwrite default queryset to filter certain files to index."""
         queryset = super().get_queryset()
 
-        # Do not index files that belong to non sphinx project
-        # Also do not index certain files
-        queryset = queryset.internal().filter(
-            project__documentation_type__contains='sphinx'
-        )
+        # Do not index files from external versions
+        queryset = queryset.internal().all()
 
         # TODO: Make this smarter
         # This was causing issues excluding some valid user documentation pages
diff --git a/readthedocs/search/parse_json.py b/readthedocs/search/parse_json.py
index 6bc5659a581..e703321e89f 100644
--- a/readthedocs/search/parse_json.py
+++ b/readthedocs/search/parse_json.py
@@ -1,6 +1,7 @@
 """Functions related to converting content into dict/JSON structures."""
 
 import logging
+from urllib.parse import urlparse
 import orjson as json
 
 from django.conf import settings
@@ -195,5 +196,56 @@ def parse_content(content, remove_first_line=False):
         content = content[1:]
 
     # converting newlines to ". "
-    content = ' '.join([text.strip() for text in content if text])
+    content = ' '.join(text.strip() for text in content if text)
     return content
+
+
+def process_mkdocs_index_file(json_storage_path, page):
+    """Reads the json index file and parses it into a structured dict."""
+    log.debug('Processing JSON index file: %s', json_storage_path)
+
+    storage = get_storage_class(settings.RTD_BUILD_MEDIA_STORAGE)()
+    try:
+        with storage.open(json_storage_path, mode='r') as f:
+            file_contents = f.read()
+    except IOError:
+        log.info('Unable to read file: %s', json_storage_path)
+        raise
+
+    data = json.loads(file_contents)
+    page_data = {}
+
+    for section in data.get('docs', []):
+        parsed_path = urlparse(section.get('location', ''))
+        fragment = parsed_path.fragment
+        path = parsed_path.path
+
+        # Some old versions of mkdocs
+        # index the pages as ``/page.html`` insted of ``page.html``.
+        path = path.lstrip('/')
+
+        if path == '' or path.endswith('/'):
+            path += 'index.html'
+
+        if page != path:
+            continue
+
+        title = HTMLParser(section.get('title')).text()
+        content = parse_content(
+            HTMLParser(section.get('text')).text()
+        )
+
+        if not fragment:
+            page_data.update({
+                'path': path,
+                'title': title,
+                'domain_data': {},
+            })
+        else:
+            page_data.setdefault('sections', []).append({
+                'id': fragment,
+                'title': title,
+                'content': content,
+            })
+
+    return page_data
diff --git a/readthedocs/search/tests/conftest.py b/readthedocs/search/tests/conftest.py
index 450959033c9..1705118b380 100644
--- a/readthedocs/search/tests/conftest.py
+++ b/readthedocs/search/tests/conftest.py
@@ -14,7 +14,7 @@
 from .dummy_data import ALL_PROJECTS, PROJECT_DATA_FILES
 
 
-@pytest.fixture()
+@pytest.fixture
 def es_index():
     call_command('search_index', '--delete', '-f')
     call_command('search_index', '--create')
@@ -23,7 +23,7 @@ def es_index():
     call_command('search_index', '--delete', '-f')
 
 
-@pytest.fixture(autouse=True)
+@pytest.fixture
 def all_projects(es_index, mock_processed_json, db, settings):
     settings.ELASTICSEARCH_DSL_AUTOSYNC = True
     projects_list = []
@@ -95,7 +95,7 @@ def get_dummy_processed_json(instance):
             return json.load(f)
 
 
-@pytest.fixture(autouse=True)
+@pytest.fixture
 def mock_processed_json(mocker):
     mocked_function = mocker.patch.object(HTMLFile, 'get_processed_json', autospec=True)
     mocked_function.side_effect = get_dummy_processed_json
diff --git a/readthedocs/search/tests/data/mkdocs/in/search_index.json b/readthedocs/search/tests/data/mkdocs/in/search_index.json
new file mode 100644
index 00000000000..3d1988872ea
--- /dev/null
+++ b/readthedocs/search/tests/data/mkdocs/in/search_index.json
@@ -0,0 +1,31 @@
+{
+  "config": {
+    "lang": [
+      "en"
+    ],
+    "prebuild_index": false,
+    "separator": "[\\s\\-]+"
+  },
+  "docs": [
+    {
+      "location": "",
+      "text": "Read the Docs MkDocs Test Project This is a test of MkDocs as it appears on Read the Docs.",
+      "title": "Read the Docs MkDocs Test Project"
+    },
+    {
+      "location": "#read-the-docs-mkdocs-test-project",
+      "text": "Read the Docs MkDocs Test Project This is a test of MkDocs as it appears on Read the Docs.",
+      "title": "Read the Docs MkDocs Test Project"
+    },
+    {
+      "location": "versions/",
+      "text": "Versions & Themes There are a number of versions and themes for mkdocs.",
+      "title": "Versions & Themes"
+    },
+    {
+      "location": "versions/#versions-themes",
+      "text": "Versions & Themes There are a number of versions and themes for mkdocs.",
+      "title": "Versions & Themes"
+    }
+  ]
+}
diff --git a/readthedocs/search/tests/data/mkdocs/in/search_index_old.json b/readthedocs/search/tests/data/mkdocs/in/search_index_old.json
new file mode 100644
index 00000000000..29a3b63811b
--- /dev/null
+++ b/readthedocs/search/tests/data/mkdocs/in/search_index_old.json
@@ -0,0 +1,24 @@
+{
+  "docs": [
+    {
+      "location": "/",
+      "text": "Read the Docs MkDocs Test Project\n\n\nThis is a test of \nMkDocs\n as it appears on \nRead the Docs\n.",
+      "title": "Read the Docs MkDocs Test Project"
+    },
+    {
+      "location": "/#read-the-docs-mkdocs-test-project",
+      "text": "Read the Docs MkDocs Test Project\n\n\nThis is a test of \nMkDocs\n as it appears on \nRead the Docs\n.",
+      "title": "Read the Docs MkDocs Test Project"
+    },
+    {
+      "location": "/versions/",
+      "text": "Versions & Themes\n\n\nThere are a number of versions and themes for mkdocs.",
+      "title": "Versions & Themes"
+    },
+    {
+      "location": "/versions/#versions-themes",
+      "text": "Versions & Themes\n\n\nThere are a number of versions and themes for mkdocs.",
+      "title": "Versions & Themes"
+    }
+  ]
+}
diff --git a/readthedocs/search/tests/data/mkdocs/out/search_index.json b/readthedocs/search/tests/data/mkdocs/out/search_index.json
new file mode 100644
index 00000000000..a9621131697
--- /dev/null
+++ b/readthedocs/search/tests/data/mkdocs/out/search_index.json
@@ -0,0 +1,26 @@
+[
+  {
+    "title": "Read the Docs MkDocs Test Project",
+    "path": "index.html",
+    "sections": [
+      {
+        "id": "read-the-docs-mkdocs-test-project",
+        "title": "Read the Docs MkDocs Test Project",
+        "content": "Read the Docs MkDocs Test Project This is a test of MkDocs as it appears on Read the Docs."
+      }
+    ],
+    "domain_data": {}
+  },
+  {
+    "title": "Versions & Themes",
+    "path": "versions/index.html",
+    "sections": [
+      {
+        "id": "versions-themes",
+        "title": "Versions & Themes",
+        "content": "Versions & Themes There are a number of versions and themes for mkdocs."
+      }
+    ],
+    "domain_data": {}
+  }
+]
diff --git a/readthedocs/search/tests/data/mkdocs/out/search_index_old.json b/readthedocs/search/tests/data/mkdocs/out/search_index_old.json
new file mode 100644
index 00000000000..16483016b42
--- /dev/null
+++ b/readthedocs/search/tests/data/mkdocs/out/search_index_old.json
@@ -0,0 +1,26 @@
+[
+  {
+    "title": "Read the Docs MkDocs Test Project",
+    "path": "index.html",
+    "sections": [
+      {
+        "id": "read-the-docs-mkdocs-test-project",
+        "title": "Read the Docs MkDocs Test Project",
+        "content": "Read the Docs MkDocs Test Project This is a test of MkDocs as it appears on Read the Docs ."
+      }
+    ],
+    "domain_data": {}
+  },
+  {
+    "title": "Versions & Themes",
+    "path": "versions/index.html",
+    "sections": [
+      {
+        "id": "versions-themes",
+        "title": "Versions & Themes",
+        "content": "Versions & Themes There are a number of versions and themes for mkdocs."
+      }
+    ],
+    "domain_data": {}
+  }
+]
diff --git a/readthedocs/search/tests/test_api.py b/readthedocs/search/tests/test_api.py
index aea84e5c782..a258545b29c 100644
--- a/readthedocs/search/tests/test_api.py
+++ b/readthedocs/search/tests/test_api.py
@@ -19,6 +19,7 @@
 
 @pytest.mark.django_db
 @pytest.mark.search
+@pytest.mark.usefixtures("all_projects")
 class BaseTestDocumentSearch:
 
     def setup_method(self, method):
diff --git a/readthedocs/search/tests/test_parse_json.py b/readthedocs/search/tests/test_parse_json.py
new file mode 100644
index 00000000000..704be9fa1e7
--- /dev/null
+++ b/readthedocs/search/tests/test_parse_json.py
@@ -0,0 +1,92 @@
+import json
+from contextlib import contextmanager
+from pathlib import Path
+from unittest import mock
+
+import pytest
+from django_dynamic_fixture import get
+
+from readthedocs.builds.storage import BuildMediaFileSystemStorage
+from readthedocs.projects.constants import MKDOCS
+from readthedocs.projects.models import HTMLFile, Project
+
+data_path = Path(__file__).parent.resolve() / 'data'
+
+
+@pytest.mark.django_db
+@pytest.mark.search
+class TestParseJSON:
+
+    def setup_method(self):
+        self.project = get(
+            Project,
+            slug='test',
+            main_language_project=None,
+        )
+        self.version = self.project.versions.first()
+
+    def _mock_open(self, content):
+        @contextmanager
+        def f(*args, **kwargs):
+            read_mock = mock.MagicMock()
+            read_mock.read.return_value = content
+            yield read_mock
+        return f
+
+    @mock.patch.object(BuildMediaFileSystemStorage, 'exists')
+    @mock.patch.object(BuildMediaFileSystemStorage, 'open')
+    def test_mkdocs(self, storage_open, storage_exists):
+        json_file = data_path / 'mkdocs/in/search_index.json'
+        storage_open.side_effect = self._mock_open(
+            json_file.open().read()
+        )
+        storage_exists.return_value = True
+
+        self.version.documentation_type = MKDOCS
+        self.version.save()
+
+        index_file = get(
+            HTMLFile,
+            project=self.project,
+            version=self.version,
+            path='index.html',
+        )
+        versions_file = get(
+            HTMLFile,
+            project=self.project,
+            version=self.version,
+            path='versions/index.html',
+        )
+
+        parsed_json = [index_file.processed_json, versions_file.processed_json]
+        expected_json = json.load(open(data_path / 'mkdocs/out/search_index.json'))
+        assert parsed_json == expected_json
+
+    @mock.patch.object(BuildMediaFileSystemStorage, 'exists')
+    @mock.patch.object(BuildMediaFileSystemStorage, 'open')
+    def test_mkdocs_old_version(self, storage_open, storage_exists):
+        json_file = data_path / 'mkdocs/in/search_index_old.json'
+        storage_open.side_effect = self._mock_open(
+            json_file.open().read()
+        )
+        storage_exists.return_value = True
+
+        self.version.documentation_type = MKDOCS
+        self.version.save()
+
+        index_file = get(
+            HTMLFile,
+            project=self.project,
+            version=self.version,
+            path='index.html',
+        )
+        versions_file = get(
+            HTMLFile,
+            project=self.project,
+            version=self.version,
+            path='versions/index.html',
+        )
+
+        parsed_json = [index_file.processed_json, versions_file.processed_json]
+        expected_json = json.load(open(data_path / 'mkdocs/out/search_index_old.json'))
+        assert parsed_json == expected_json
diff --git a/readthedocs/search/tests/test_search_tasks.py b/readthedocs/search/tests/test_search_tasks.py
index 75c01e35eeb..92501dfd367 100644
--- a/readthedocs/search/tests/test_search_tasks.py
+++ b/readthedocs/search/tests/test_search_tasks.py
@@ -14,6 +14,7 @@
 
 @pytest.mark.django_db
 @pytest.mark.search
+@pytest.mark.usefixtures("all_projects")
 class TestSearchTasks:
 
     @classmethod
diff --git a/readthedocs/search/tests/test_views.py b/readthedocs/search/tests/test_views.py
index 8ae7d9e4631..648f029e960 100644
--- a/readthedocs/search/tests/test_views.py
+++ b/readthedocs/search/tests/test_views.py
@@ -86,6 +86,7 @@ def test_search_project_filter_language(self, client, project):
 
 @pytest.mark.django_db
 @pytest.mark.search
+@pytest.mark.usefixtures("all_projects")
 class TestPageSearch:
 
     @pytest.fixture(autouse=True)
diff --git a/readthedocs/search/tests/utils.py b/readthedocs/search/tests/utils.py
index d3cf1530996..8a82a42ccc5 100644
--- a/readthedocs/search/tests/utils.py
+++ b/readthedocs/search/tests/utils.py
@@ -1,5 +1,3 @@
-# -*- coding: utf-8 -*-
-
 import random
 
 from readthedocs.projects.models import HTMLFile