diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -2017,6 +2017,7 @@
     'PhabricatorCustomFieldEditEngineExtension' => 'infrastructure/customfield/engineextension/PhabricatorCustomFieldEditEngineExtension.php',
     'PhabricatorCustomFieldEditField' => 'infrastructure/customfield/editor/PhabricatorCustomFieldEditField.php',
     'PhabricatorCustomFieldEditType' => 'infrastructure/customfield/editor/PhabricatorCustomFieldEditType.php',
+    'PhabricatorCustomFieldFulltextEngineExtension' => 'infrastructure/customfield/engineextension/PhabricatorCustomFieldFulltextEngineExtension.php',
     'PhabricatorCustomFieldHeraldField' => 'infrastructure/customfield/herald/PhabricatorCustomFieldHeraldField.php',
     'PhabricatorCustomFieldHeraldFieldGroup' => 'infrastructure/customfield/herald/PhabricatorCustomFieldHeraldFieldGroup.php',
     'PhabricatorCustomFieldImplementationIncompleteException' => 'infrastructure/customfield/exception/PhabricatorCustomFieldImplementationIncompleteException.php',
@@ -2326,6 +2327,8 @@
     'PhabricatorFlaggableInterface' => 'applications/flag/interface/PhabricatorFlaggableInterface.php',
     'PhabricatorFlagsApplication' => 'applications/flag/application/PhabricatorFlagsApplication.php',
     'PhabricatorFlagsUIEventListener' => 'applications/flag/events/PhabricatorFlagsUIEventListener.php',
+    'PhabricatorFulltextEngineExtension' => 'applications/search/index/PhabricatorFulltextEngineExtension.php',
+    'PhabricatorFulltextEngineExtensionModule' => 'applications/search/index/PhabricatorFulltextEngineExtensionModule.php',
     'PhabricatorFundApplication' => 'applications/fund/application/PhabricatorFundApplication.php',
     'PhabricatorGDSetupCheck' => 'applications/config/check/PhabricatorGDSetupCheck.php',
     'PhabricatorGarbageCollector' => 'infrastructure/daemon/garbagecollector/PhabricatorGarbageCollector.php',
@@ -2870,6 +2873,7 @@
     'PhabricatorProjectWatchController' => 'applications/project/controller/PhabricatorProjectWatchController.php',
     'PhabricatorProjectsEditEngineExtension' => 'applications/project/engineextension/PhabricatorProjectsEditEngineExtension.php',
     'PhabricatorProjectsEditField' => 'applications/transactions/editfield/PhabricatorProjectsEditField.php',
+    'PhabricatorProjectsFulltextEngineExtension' => 'applications/project/engineextension/PhabricatorProjectsFulltextEngineExtension.php',
     'PhabricatorProjectsPolicyRule' => 'applications/project/policyrule/PhabricatorProjectsPolicyRule.php',
     'PhabricatorProjectsSearchEngineAttachment' => 'applications/project/engineextension/PhabricatorProjectsSearchEngineAttachment.php',
     'PhabricatorProjectsSearchEngineExtension' => 'applications/project/engineextension/PhabricatorProjectsSearchEngineExtension.php',
@@ -3168,6 +3172,7 @@
     'PhabricatorSubscriptionsEditController' => 'applications/subscriptions/controller/PhabricatorSubscriptionsEditController.php',
     'PhabricatorSubscriptionsEditEngineExtension' => 'applications/subscriptions/engineextension/PhabricatorSubscriptionsEditEngineExtension.php',
     'PhabricatorSubscriptionsEditor' => 'applications/subscriptions/editor/PhabricatorSubscriptionsEditor.php',
+    'PhabricatorSubscriptionsFulltextEngineExtension' => 'applications/subscriptions/engineextension/PhabricatorSubscriptionsFulltextEngineExtension.php',
     'PhabricatorSubscriptionsHeraldAction' => 'applications/subscriptions/herald/PhabricatorSubscriptionsHeraldAction.php',
     'PhabricatorSubscriptionsListController' => 'applications/subscriptions/controller/PhabricatorSubscriptionsListController.php',
     'PhabricatorSubscriptionsRemoveSelfHeraldAction' => 'applications/subscriptions/herald/PhabricatorSubscriptionsRemoveSelfHeraldAction.php',
@@ -6177,6 +6182,7 @@
     'PhabricatorCustomFieldEditEngineExtension' => 'PhabricatorEditEngineExtension',
     'PhabricatorCustomFieldEditField' => 'PhabricatorEditField',
     'PhabricatorCustomFieldEditType' => 'PhabricatorEditType',
+    'PhabricatorCustomFieldFulltextEngineExtension' => 'PhabricatorFulltextEngineExtension',
     'PhabricatorCustomFieldHeraldField' => 'HeraldField',
     'PhabricatorCustomFieldHeraldFieldGroup' => 'HeraldFieldGroup',
     'PhabricatorCustomFieldImplementationIncompleteException' => 'Exception',
@@ -6543,6 +6549,8 @@
     'PhabricatorFlaggableInterface' => 'PhabricatorPHIDInterface',
     'PhabricatorFlagsApplication' => 'PhabricatorApplication',
     'PhabricatorFlagsUIEventListener' => 'PhabricatorEventListener',
+    'PhabricatorFulltextEngineExtension' => 'Phobject',
+    'PhabricatorFulltextEngineExtensionModule' => 'PhabricatorConfigModule',
     'PhabricatorFundApplication' => 'PhabricatorApplication',
     'PhabricatorGDSetupCheck' => 'PhabricatorSetupCheck',
     'PhabricatorGarbageCollector' => 'Phobject',
@@ -7176,6 +7184,7 @@
     'PhabricatorProjectWatchController' => 'PhabricatorProjectController',
     'PhabricatorProjectsEditEngineExtension' => 'PhabricatorEditEngineExtension',
     'PhabricatorProjectsEditField' => 'PhabricatorTokenizerEditField',
+    'PhabricatorProjectsFulltextEngineExtension' => 'PhabricatorFulltextEngineExtension',
     'PhabricatorProjectsPolicyRule' => 'PhabricatorPolicyRule',
     'PhabricatorProjectsSearchEngineAttachment' => 'PhabricatorSearchEngineAttachment',
     'PhabricatorProjectsSearchEngineExtension' => 'PhabricatorSearchEngineExtension',
@@ -7530,6 +7539,7 @@
     'PhabricatorSubscriptionsEditController' => 'PhabricatorController',
     'PhabricatorSubscriptionsEditEngineExtension' => 'PhabricatorEditEngineExtension',
     'PhabricatorSubscriptionsEditor' => 'PhabricatorEditor',
+    'PhabricatorSubscriptionsFulltextEngineExtension' => 'PhabricatorFulltextEngineExtension',
     'PhabricatorSubscriptionsHeraldAction' => 'HeraldAction',
     'PhabricatorSubscriptionsListController' => 'PhabricatorController',
     'PhabricatorSubscriptionsRemoveSelfHeraldAction' => 'PhabricatorSubscriptionsHeraldAction',
diff --git a/src/applications/project/engineextension/PhabricatorProjectsFulltextEngineExtension.php b/src/applications/project/engineextension/PhabricatorProjectsFulltextEngineExtension.php
new file mode 100644
--- /dev/null
+++ b/src/applications/project/engineextension/PhabricatorProjectsFulltextEngineExtension.php
@@ -0,0 +1,37 @@
+<?php
+
+final class PhabricatorProjectsFulltextEngineExtension
+  extends PhabricatorFulltextEngineExtension {
+
+  const EXTENSIONKEY = 'projects';
+
+  public function getExtensionName() {
+    return pht('Projects');
+  }
+
+  public function shouldIndexFulltextObject($object) {
+    return ($object instanceof PhabricatorProjectInterface);
+  }
+
+  public function indexFulltextObject(
+    $object,
+    PhabricatorSearchAbstractDocument $document) {
+
+    $project_phids = PhabricatorEdgeQuery::loadDestinationPHIDs(
+      $object->getPHID(),
+      PhabricatorProjectObjectHasProjectEdgeType::EDGECONST);
+
+    if (!$project_phids) {
+      return;
+    }
+
+    foreach ($project_phids as $project_phid) {
+      $document->addRelationship(
+        PhabricatorSearchRelationship::RELATIONSHIP_PROJECT,
+        $project_phid,
+        PhabricatorProjectProjectPHIDType::TYPECONST,
+        $document->getDocumentModified()); // Bogus timestamp.
+    }
+  }
+
+}
diff --git a/src/applications/search/index/PhabricatorFulltextEngineExtension.php b/src/applications/search/index/PhabricatorFulltextEngineExtension.php
new file mode 100644
--- /dev/null
+++ b/src/applications/search/index/PhabricatorFulltextEngineExtension.php
@@ -0,0 +1,28 @@
+<?php
+
+abstract class PhabricatorFulltextEngineExtension extends Phobject {
+
+  final public function getExtensionKey() {
+    return $this->getPhobjectClassConstant('EXTENSIONKEY');
+  }
+
+  final protected function getViewer() {
+    return PhabricatorUser::getOmnipotentUser();
+  }
+
+  abstract public function getExtensionName();
+
+  abstract public function shouldIndexFulltextObject($object);
+
+  abstract public function indexFulltextObject(
+    $object,
+    PhabricatorSearchAbstractDocument $document);
+
+  final public static function getAllExtensions() {
+    return id(new PhutilClassMapQuery())
+      ->setAncestorClass(__CLASS__)
+      ->setUniqueMethod('getExtensionKey')
+      ->execute();
+  }
+
+}
diff --git a/src/applications/search/index/PhabricatorFulltextEngineExtensionModule.php b/src/applications/search/index/PhabricatorFulltextEngineExtensionModule.php
new file mode 100644
--- /dev/null
+++ b/src/applications/search/index/PhabricatorFulltextEngineExtensionModule.php
@@ -0,0 +1,44 @@
+<?php
+
+final class PhabricatorFulltextEngineExtensionModule
+  extends PhabricatorConfigModule {
+
+  public function getModuleKey() {
+    return 'fulltextengine';
+  }
+
+  public function getModuleName() {
+    return pht('Engine: Fulltext');
+  }
+
+  public function renderModuleStatus(AphrontRequest $request) {
+    $viewer = $request->getViewer();
+
+    $extensions = PhabricatorFulltextEngineExtension::getAllExtensions();
+
+    $rows = array();
+    foreach ($extensions as $extension) {
+      $rows[] = array(
+        get_class($extension),
+        $extension->getExtensionName(),
+      );
+    }
+
+    $table = id(new AphrontTableView($rows))
+      ->setHeaders(
+        array(
+          pht('Class'),
+          pht('Name'),
+        ))
+      ->setColumnClasses(
+        array(
+          null,
+          'wide pri',
+        ));
+
+    return id(new PHUIObjectBoxView())
+      ->setHeaderText(pht('FulltextEngine Extensions'))
+      ->setTable($table);
+  }
+
+}
diff --git a/src/applications/search/index/PhabricatorSearchDocumentIndexer.php b/src/applications/search/index/PhabricatorSearchDocumentIndexer.php
--- a/src/applications/search/index/PhabricatorSearchDocumentIndexer.php
+++ b/src/applications/search/index/PhabricatorSearchDocumentIndexer.php
@@ -52,20 +52,15 @@
 
     $object = $this->loadDocumentByPHID($phid);
 
-    // Automatically rebuild CustomField indexes if the object uses custom
-    // fields.
-    if ($object instanceof PhabricatorCustomFieldInterface) {
-      $this->indexCustomFields($document, $object);
-    }
-
-    // Automatically rebuild subscriber indexes if the object is subscribable.
-    if ($object instanceof PhabricatorSubscribableInterface) {
-      $this->indexSubscribers($document);
+    $extensions = PhabricatorFulltextEngineExtension::getAllExtensions();
+    foreach ($extensions as $key => $extension) {
+      if (!$extension->shouldIndexFulltextObject($object)) {
+        unset($extensions[$key]);
+      }
     }
 
-    // Automatically build project relationships
-    if ($object instanceof PhabricatorProjectInterface) {
-      $this->indexProjects($document, $object);
+    foreach ($extensions as $extension) {
+      $extension->indexFulltextObject($object, $document);
     }
 
     $engine = PhabricatorSearchEngine::loadEngine();
@@ -82,43 +77,6 @@
       ->setDocumentType(phid_get_type($phid));
   }
 
-  protected function indexSubscribers(
-    PhabricatorSearchAbstractDocument $doc) {
-
-    $subscribers = PhabricatorSubscribersQuery::loadSubscribersForPHID(
-      $doc->getPHID());
-    $handles = id(new PhabricatorHandleQuery())
-      ->setViewer($this->getViewer())
-      ->withPHIDs($subscribers)
-      ->execute();
-
-    foreach ($handles as $phid => $handle) {
-      $doc->addRelationship(
-        PhabricatorSearchRelationship::RELATIONSHIP_SUBSCRIBER,
-        $phid,
-        $handle->getType(),
-        $doc->getDocumentModified()); // Bogus timestamp.
-    }
-  }
-
-  protected function indexProjects(
-    PhabricatorSearchAbstractDocument $doc,
-    PhabricatorProjectInterface $object) {
-
-    $project_phids = PhabricatorEdgeQuery::loadDestinationPHIDs(
-      $object->getPHID(),
-      PhabricatorProjectObjectHasProjectEdgeType::EDGECONST);
-    if ($project_phids) {
-      foreach ($project_phids as $project_phid) {
-        $doc->addRelationship(
-          PhabricatorSearchRelationship::RELATIONSHIP_PROJECT,
-          $project_phid,
-          PhabricatorProjectProjectPHIDType::TYPECONST,
-          $doc->getDocumentModified()); // Bogus timestamp.
-      }
-    }
-  }
-
   protected function indexTransactions(
     PhabricatorSearchAbstractDocument $doc,
     PhabricatorApplicationTransactionQuery $query,
@@ -141,28 +99,6 @@
     }
   }
 
-  protected function indexCustomFields(
-    PhabricatorSearchAbstractDocument $document,
-    PhabricatorCustomFieldInterface $object) {
-
-    // Rebuild the ApplicationSearch indexes. These are internal and not part of
-    // the fulltext search, but putting them in this workflow allows users to
-    // use the same tools to rebuild the indexes, which is easy to understand.
-
-    $field_list = PhabricatorCustomField::getObjectFields(
-      $object,
-      PhabricatorCustomField::ROLE_DEFAULT);
-
-    $field_list->setViewer($this->getViewer());
-    $field_list->readFieldsFromStorage($object);
-
-    // Rebuild ApplicationSearch indexes.
-    $field_list->rebuildIndexes($object);
-
-    // Rebuild global search indexes.
-    $field_list->updateAbstractDocument($document);
-  }
-
   private function dispatchDidUpdateIndexEvent(
     $phid,
     PhabricatorSearchAbstractDocument $document) {
diff --git a/src/applications/subscriptions/engineextension/PhabricatorSubscriptionsFulltextEngineExtension.php b/src/applications/subscriptions/engineextension/PhabricatorSubscriptionsFulltextEngineExtension.php
new file mode 100644
--- /dev/null
+++ b/src/applications/subscriptions/engineextension/PhabricatorSubscriptionsFulltextEngineExtension.php
@@ -0,0 +1,41 @@
+<?php
+
+final class PhabricatorSubscriptionsFulltextEngineExtension
+  extends PhabricatorFulltextEngineExtension {
+
+  const EXTENSIONKEY = 'subscriptions';
+
+  public function getExtensionName() {
+    return pht('Subscribers');
+  }
+
+  public function shouldIndexFulltextObject($object) {
+    return ($object instanceof PhabricatorSubscribableInterface);
+  }
+
+  public function indexFulltextObject(
+    $object,
+    PhabricatorSearchAbstractDocument $document) {
+
+    $subscriber_phids = PhabricatorSubscribersQuery::loadSubscribersForPHID(
+      $object->getPHID());
+
+    if (!$subscriber_phids) {
+      return;
+    }
+
+    $handles = id(new PhabricatorHandleQuery())
+      ->setViewer($this->getViewer())
+      ->withPHIDs($subscriber_phids)
+      ->execute();
+
+    foreach ($handles as $phid => $handle) {
+      $document->addRelationship(
+        PhabricatorSearchRelationship::RELATIONSHIP_SUBSCRIBER,
+        $phid,
+        $handle->getType(),
+        $document->getDocumentModified()); // Bogus timestamp.
+    }
+  }
+
+}
diff --git a/src/infrastructure/customfield/engineextension/PhabricatorCustomFieldFulltextEngineExtension.php b/src/infrastructure/customfield/engineextension/PhabricatorCustomFieldFulltextEngineExtension.php
new file mode 100644
--- /dev/null
+++ b/src/infrastructure/customfield/engineextension/PhabricatorCustomFieldFulltextEngineExtension.php
@@ -0,0 +1,39 @@
+<?php
+
+final class PhabricatorCustomFieldFulltextEngineExtension
+  extends PhabricatorFulltextEngineExtension {
+
+  const EXTENSIONKEY = 'customfield.fields';
+
+  public function getExtensionName() {
+    return pht('Custom Fields');
+  }
+
+  public function shouldIndexFulltextObject($object) {
+    return ($object instanceof PhabricatorCustomFieldInterface);
+  }
+
+  public function indexFulltextObject(
+    $object,
+    PhabricatorSearchAbstractDocument $document) {
+
+    // Rebuild the ApplicationSearch indexes. These are internal and not part
+    // of the fulltext search, but putting them in this workflow allows users
+    // to use the same tools to rebuild the indexes, which is easy to
+    // understand.
+
+    $field_list = PhabricatorCustomField::getObjectFields(
+      $object,
+      PhabricatorCustomField::ROLE_DEFAULT);
+
+    $field_list->setViewer($this->getViewer());
+    $field_list->readFieldsFromStorage($object);
+
+    // Rebuild ApplicationSearch indexes.
+    $field_list->rebuildIndexes($object);
+
+    // Rebuild global search indexes.
+    $field_list->updateAbstractDocument($document);
+  }
+
+}