diff --git a/core/includes/file.inc b/core/includes/file.inc
index 3e5eb8c..d241e15 100644
--- a/core/includes/file.inc
+++ b/core/includes/file.inc
@@ -10,6 +10,7 @@
 use Drupal\Component\PhpStorage\FileStorage;
 use Drupal\Component\Utility\Bytes;
 use Drupal\Core\File\FileSystem;
+use Drupal\Core\Site\Settings;
 use Drupal\Core\StreamWrapper\PublicStream;
 use Drupal\Core\StreamWrapper\PrivateStream;
 
@@ -913,7 +914,7 @@ function file_unmanaged_save_data($data, $destination = NULL, $replace = FILE_EX
  * @param $options
  *   An associative array of additional options, with the following elements:
  *   - 'nomask': The preg_match() regular expression for files to be excluded.
- *     There is no default.
+ *     Defaults to the 'file_scan_ignore_directories' setting.
  *   - 'callback': The callback function to call for each match. There is no
  *     default callback.
  *   - 'recurse': When TRUE, the directory scan will recurse the entire tree
@@ -946,6 +947,18 @@ function file_scan_directory($dir, $mask, $options = array(), $depth = 0) {
     $dir_has_slash = (substr($dir, -1) === '/');
   }
 
+  // Allow directories specified in settings.php to be ignored. You can use this
+  // to not check for files in common special-purpose directories. For example,
+  // node_modules and bower_components. Ignoring irrelevant directories is a
+  // performance boost.
+  if (!isset($options['nomask'])) {
+    $ignore_directories = Settings::get('file_scan_ignore_directories', []);
+    array_walk($ignore_directories, function(&$value) {
+      $value = preg_quote($value, '/');
+    });
+    $default_nomask = '/^' . implode('|', $ignore_directories) . '$/';
+  }
+
   $options['key'] = in_array($options['key'], array('uri', 'filename', 'name')) ? $options['key'] : 'uri';
   $files = array();
   // Avoid warnings when opendir does not have the permissions to open a
@@ -954,7 +967,10 @@ function file_scan_directory($dir, $mask, $options = array(), $depth = 0) {
     if ($handle = @opendir($dir)) {
       while (FALSE !== ($filename = readdir($handle))) {
         // Skip this file if it matches the nomask or starts with a dot.
-        if ($filename[0] != '.' && !(isset($options['nomask']) && preg_match($options['nomask'], $filename))) {
+        if ($filename[0] != '.'
+          && !(isset($options['nomask']) && preg_match($options['nomask'], $filename))
+          && !(!empty($default_nomask) && preg_match($default_nomask, $filename))
+          ) {
           if ($depth == 0 && $dir_has_slash) {
             $uri = "$dir$filename";
           }
diff --git a/core/lib/Drupal/Core/Extension/Discovery/RecursiveExtensionFilterIterator.php b/core/lib/Drupal/Core/Extension/Discovery/RecursiveExtensionFilterIterator.php
index a74dcfc..79a2726 100644
--- a/core/lib/Drupal/Core/Extension/Discovery/RecursiveExtensionFilterIterator.php
+++ b/core/lib/Drupal/Core/Extension/Discovery/RecursiveExtensionFilterIterator.php
@@ -87,6 +87,20 @@ class RecursiveExtensionFilterIterator extends \RecursiveFilterIterator {
   protected $acceptTests = FALSE;
 
   /**
+   * Construct a RecursiveExtensionFilterIterator.
+   *
+   * @param \RecursiveIterator $iterator
+   *   The iterator to filter.
+   * @param array $blacklist
+   *   (optional) Add to the blacklist of directories that should be filtered
+   *   out during the iteration.
+   */
+  public function __construct(\RecursiveIterator $iterator, array $blacklist = []) {
+    parent::__construct($iterator);
+    $this->blacklist = array_merge($this->blacklist, $blacklist);
+  }
+
+  /**
    * Controls whether test directories will be scanned.
    *
    * @param bool $flag
@@ -107,6 +121,8 @@ public function acceptTests($flag = FALSE) {
    */
   public function getChildren() {
     $filter = parent::getChildren();
+    // Pass on the blacklist.
+    $filter->blacklist = $this->blacklist;
     // Pass the $acceptTests flag forward to child iterators.
     $filter->acceptTests($this->acceptTests);
     return $filter;
diff --git a/core/lib/Drupal/Core/Extension/ExtensionDiscovery.php b/core/lib/Drupal/Core/Extension/ExtensionDiscovery.php
index 3d68561..9da0b01 100644
--- a/core/lib/Drupal/Core/Extension/ExtensionDiscovery.php
+++ b/core/lib/Drupal/Core/Extension/ExtensionDiscovery.php
@@ -433,11 +433,17 @@ protected function scanDirectory($dir, $include_tests) {
     $flags |= \FilesystemIterator::CURRENT_AS_SELF;
     $directory_iterator = new \RecursiveDirectoryIterator($absolute_dir, $flags);
 
+    // Allow directories specified in settings.php to be ignored. You can use
+    // this to not check for files in common special-purpose directories. For
+    // example, node_modules and bower_components. Ignoring irrelevant
+    // directories is a performance boost.
+    $ignore_directories = Settings::get('file_scan_ignore_directories', []);
+
     // Filter the recursive scan to discover extensions only.
     // Important: Without a RecursiveFilterIterator, RecursiveDirectoryIterator
     // would recurse into the entire filesystem directory tree without any kind
     // of limitations.
-    $filter = new RecursiveExtensionFilterIterator($directory_iterator);
+    $filter = new RecursiveExtensionFilterIterator($directory_iterator, $ignore_directories);
     $filter->acceptTests($include_tests);
 
     // The actual recursive filesystem scan is only invoked by instantiating the
diff --git a/core/modules/system/src/Tests/Common/SystemListingTest.php b/core/modules/system/src/Tests/Common/SystemListingTest.php
index a9d1549..ec3fcda 100644
--- a/core/modules/system/src/Tests/Common/SystemListingTest.php
+++ b/core/modules/system/src/Tests/Common/SystemListingTest.php
@@ -55,4 +55,27 @@ function testDirectoryPrecedence() {
       )));
     }
   }
+
+  /**
+   * Tests that directories matching file_scan_ignore_directories are ignored
+   */
+  function testFileScanIgnoreDirectory() {
+    $listing = new ExtensionDiscovery(\Drupal::root(), FALSE);
+    $listing->setProfileDirectories(array('core/profiles/testing'));
+    $files = $listing->scan('module');
+    $this->assertTrue(isset($files['drupal_system_listing_compatible_test']));
+
+    // Reset the static to force a rescan of the directories.
+    $reflected_class = new \ReflectionClass(ExtensionDiscovery::class);
+    $reflected_property = $reflected_class->getProperty('files');
+    $reflected_property->setAccessible(true);
+    $reflected_property->setValue($reflected_class, []);
+
+    $this->settingsSet('file_scan_ignore_directories', ['drupal_system_listing_compatible_test']);
+    $listing = new ExtensionDiscovery(\Drupal::root(), FALSE);
+    $listing->setProfileDirectories(array('core/profiles/testing'));
+    $files = $listing->scan('module');
+    $this->assertFalse(isset($files['drupal_system_listing_compatible_test']));
+  }
+
 }
diff --git a/core/modules/system/src/Tests/File/ScanDirectoryTest.php b/core/modules/system/src/Tests/File/ScanDirectoryTest.php
index 4b067f0..9c85d16 100644
--- a/core/modules/system/src/Tests/File/ScanDirectoryTest.php
+++ b/core/modules/system/src/Tests/File/ScanDirectoryTest.php
@@ -146,4 +146,26 @@ function testOptionMinDepth() {
     $files = file_scan_directory($this->path, '/^javascript-/', array('min_depth' => 1));
     $this->assertTrue(empty($files), 'Minimum-depth of 1 successfully excludes files from current directory.');
   }
+
+  /**
+   * Tests file_scan_directory() obeys 'file_scan_ignore_directories' setting.
+   */
+  function testIgnoreDirectories() {
+    $files = file_scan_directory('core/modules/system/tests/fixtures/IgnoreDirectories', '/\.txt$/');
+    $this->assertEqual(2, count($files), '2 text files found when not ignoring directories.');
+
+    $this->settingsSet('file_scan_ignore_directories', ['frontend_framework']);
+    $files = file_scan_directory('core/modules/system/tests/fixtures/IgnoreDirectories', '/\.txt$/');
+    $this->assertEqual(1, count($files), '1 text files found when ignoring directories called "frontend_framework".');
+
+    // Ensure that the directories in file_scan_ignore_directories are escaped
+    // using preg_quote.
+    $this->settingsSet('file_scan_ignore_directories', ['frontend.*']);
+    $files = file_scan_directory('core/modules/system/tests/fixtures/IgnoreDirectories', '/\.txt$/');
+    $this->assertEqual(2, count($files), '2 text files found when ignoring a directory that is not there.');
+
+    $files = file_scan_directory('core/modules/system/tests/fixtures/IgnoreDirectories', '/\.txt$/', ['nomask' => '/^something_thing_else$/']);
+    $this->assertEqual(2, count($files), '2 text files found when an "nomasl" option passed in.');
+  }
+
 }
diff --git a/core/modules/system/tests/fixtures/IgnoreDirectories/a.txt b/core/modules/system/tests/fixtures/IgnoreDirectories/a.txt
new file mode 100644
index 0000000..e69de29
diff --git a/core/modules/system/tests/fixtures/IgnoreDirectories/frontend_framework/b.txt b/core/modules/system/tests/fixtures/IgnoreDirectories/frontend_framework/b.txt
new file mode 100644
index 0000000..e69de29
diff --git a/sites/default/default.settings.php b/sites/default/default.settings.php
index 7f28c29..c99aba9 100644
--- a/sites/default/default.settings.php
+++ b/sites/default/default.settings.php
@@ -705,6 +705,21 @@
  */
 
 /**
+ * The default list of directories that will be ignored by Drupal's file API's.
+ *
+ * By default ignore node_modules and bower_components folders to avoid issues
+ * with common frontend tools and recursive scanning of directories looking for
+ * extensions.
+ *
+ * @see file_scan_directory()
+ * @see \Drupal\Core\Extension\ExtensionDiscovery::scanDirectory()
+ */
+$settings['file_scan_ignore_directories'] = [
+  'node_modules',
+  'bower_components',
+];
+
+/**
  * Load local development override configuration, if available.
  *
  * Use settings.local.php to override variables on secondary (staging,