diff --git a/core/config/schema/core.data_types.schema.yml b/core/config/schema/core.data_types.schema.yml
index cc89fa9..4968087 100644
--- a/core/config/schema/core.data_types.schema.yml
+++ b/core/config/schema/core.data_types.schema.yml
@@ -445,6 +445,9 @@ field.storage_settings.string:
     case_sensitive:
       type: boolean
       label: 'Case sensitive'
+    is_ascii:
+      type: boolean
+      label: 'Contains US ASCII characters only'
 
 field.field_settings.string:
   type: mapping
diff --git a/core/lib/Drupal/Core/Cache/DatabaseBackend.php b/core/lib/Drupal/Core/Cache/DatabaseBackend.php
index b1144e4..27460e4 100644
--- a/core/lib/Drupal/Core/Cache/DatabaseBackend.php
+++ b/core/lib/Drupal/Core/Cache/DatabaseBackend.php
@@ -441,7 +441,7 @@ public function schemaDefinition() {
       'fields' => array(
         'cid' => array(
           'description' => 'Primary Key: Unique cache ID.',
-          'type' => 'varchar',
+          'type' => 'varchar_ascii',
           'length' => 255,
           'not null' => TRUE,
           'default' => '',
@@ -482,7 +482,7 @@ public function schemaDefinition() {
         ),
         'checksum' => array(
           'description' => 'The tag invalidation checksum when this entry was saved.',
-          'type' => 'varchar',
+          'type' => 'varchar_ascii',
           'length' => 255,
           'not null' => TRUE,
         ),
diff --git a/core/lib/Drupal/Core/Cache/DatabaseCacheTagsChecksum.php b/core/lib/Drupal/Core/Cache/DatabaseCacheTagsChecksum.php
index cc882ee..14b34ec 100644
--- a/core/lib/Drupal/Core/Cache/DatabaseCacheTagsChecksum.php
+++ b/core/lib/Drupal/Core/Cache/DatabaseCacheTagsChecksum.php
@@ -175,7 +175,7 @@ public function schemaDefinition() {
       'fields' => array(
         'tag' => array(
           'description' => 'Namespace-prefixed tag string.',
-          'type' => 'varchar',
+          'type' => 'varchar_ascii',
           'length' => 255,
           'not null' => TRUE,
           'default' => '',
diff --git a/core/lib/Drupal/Core/Config/DatabaseStorage.php b/core/lib/Drupal/Core/Config/DatabaseStorage.php
index 6c33273..646a1d5 100644
--- a/core/lib/Drupal/Core/Config/DatabaseStorage.php
+++ b/core/lib/Drupal/Core/Config/DatabaseStorage.php
@@ -192,14 +192,14 @@ protected static function schemaDefinition() {
       'fields' => array(
         'collection' => array(
           'description' => 'Primary Key: Config object collection.',
-          'type' => 'varchar',
+          'type' => 'varchar_ascii',
           'length' => 255,
           'not null' => TRUE,
           'default' => '',
         ),
         'name' => array(
           'description' => 'Primary Key: Config object name.',
-          'type' => 'varchar',
+          'type' => 'varchar_ascii',
           'length' => 255,
           'not null' => TRUE,
           'default' => '',
diff --git a/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php b/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php
index d0aba49..5cb6248 100644
--- a/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php
+++ b/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php
@@ -144,6 +144,9 @@ protected function createFieldSql($name, $spec) {
       if (!empty($spec['binary'])) {
         $sql .= ' BINARY';
       }
+      if (isset($spec['type']) && $spec['type'] == 'varchar_ascii') {
+        $sql .= ' CHARACTER SET ascii COLLATE ascii_general_ci';
+      }
     }
     elseif (isset($spec['precision']) && isset($spec['scale'])) {
       $sql .= '(' . $spec['precision'] . ', ' . $spec['scale'] . ')';
@@ -218,6 +221,8 @@ public function getFieldTypeMap() {
     // database types back into schema types.
     // $map does not use drupal_static as its value never changes.
     static $map = array(
+      'varchar_ascii:normal' => 'VARCHAR',
+
       'varchar:normal'  => 'VARCHAR',
       'char:normal'     => 'CHAR',
 
diff --git a/core/lib/Drupal/Core/Database/Driver/pgsql/Schema.php b/core/lib/Drupal/Core/Database/Driver/pgsql/Schema.php
index 506baa8..5b70b1b 100644
--- a/core/lib/Drupal/Core/Database/Driver/pgsql/Schema.php
+++ b/core/lib/Drupal/Core/Database/Driver/pgsql/Schema.php
@@ -363,6 +363,7 @@ function getFieldTypeMap() {
     // database types back into schema types.
     // $map does not use drupal_static as its value never changes.
     static $map = array(
+      'varchar_ascii:normal' => 'varchar',
       'varchar:normal' => 'varchar',
       'char:normal' => 'character',
 
diff --git a/core/lib/Drupal/Core/Database/Driver/sqlite/Schema.php b/core/lib/Drupal/Core/Database/Driver/sqlite/Schema.php
index 6673d1f..897de79 100644
--- a/core/lib/Drupal/Core/Database/Driver/sqlite/Schema.php
+++ b/core/lib/Drupal/Core/Database/Driver/sqlite/Schema.php
@@ -207,6 +207,8 @@ public function getFieldTypeMap() {
     // database types back into schema types.
     // $map does not use drupal_static as its value never changes.
     static $map = array(
+      'varchar_ascii:normal' => 'VARCHAR',
+
       'varchar:normal'  => 'VARCHAR',
       'char:normal'     => 'CHAR',
 
diff --git a/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchema.php b/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchema.php
index 6fb4ddf..b066969 100644
--- a/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchema.php
+++ b/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchema.php
@@ -1568,7 +1568,7 @@ protected function getDedicatedTableSchema(FieldStorageDefinitionInterface $stor
     }
     else {
       $id_schema = array(
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 128,
         'not null' => TRUE,
         'description' => 'The entity id this data is attached to',
@@ -1601,7 +1601,7 @@ protected function getDedicatedTableSchema(FieldStorageDefinitionInterface $stor
       'description' => $description_current,
       'fields' => array(
         'bundle' => array(
-          'type' => 'varchar',
+          'type' => 'varchar_ascii',
           'length' => 128,
           'not null' => TRUE,
           'default' => '',
@@ -1617,7 +1617,7 @@ protected function getDedicatedTableSchema(FieldStorageDefinitionInterface $stor
         'entity_id' => $id_schema,
         'revision_id' => $revision_id_schema,
         'langcode' => array(
-          'type' => 'varchar',
+          'type' => 'varchar_ascii',
           'length' => 32,
           'not null' => TRUE,
           'default' => '',
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EntityReferenceItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EntityReferenceItem.php
index ca54aa8..21d7090 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EntityReferenceItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EntityReferenceItem.php
@@ -133,7 +133,7 @@ public static function schema(FieldStorageDefinitionInterface $field_definition)
       $columns = array(
         'target_id' => array(
           'description' => 'The ID of the target entity.',
-          'type' => 'varchar',
+          'type' => 'varchar_ascii',
           // If the target entities act as bundles for another entity type,
           // their IDs should not exceed the maximum length for bundles.
           'length' => $target_type_info->getBundleOf() ? EntityTypeInterface::BUNDLE_MAX_LENGTH : 255,
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/LanguageItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/LanguageItem.php
index 9ab60a4..b7ce7fb 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/LanguageItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/LanguageItem.php
@@ -44,6 +44,7 @@ class LanguageItem extends FieldItemBase {
   public static function propertyDefinitions(FieldStorageDefinitionInterface $field_definition) {
     $properties['value'] = DataDefinition::create('string')
       ->setLabel(t('Language code'))
+      ->setSetting('is_ascii', TRUE)
       ->setRequired(TRUE);
 
     $properties['language'] = DataReferenceDefinition::create('language')
@@ -75,6 +76,7 @@ public static function schema(FieldStorageDefinitionInterface $field_definition)
         'value' => array(
           'type' => 'varchar',
           'length' => 12,
+          'is_ascii' => TRUE,
         ),
       ),
     );
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringItem.php
index 8817c87..2329c86 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringItem.php
@@ -32,6 +32,7 @@ class StringItem extends StringItemBase {
   public static function defaultStorageSettings() {
     return array(
       'max_length' => 255,
+      'is_ascii' => FALSE,
     ) + parent::defaultStorageSettings();
   }
 
@@ -42,7 +43,7 @@ public static function schema(FieldStorageDefinitionInterface $field_definition)
     return array(
       'columns' => array(
         'value' => array(
-          'type' => 'varchar',
+          'type' => $field_definition->getSetting('is_ascii') === TRUE ? 'varchar_ascii' : 'varchar',
           'length' => (int) $field_definition->getSetting('max_length'),
           'binary' => $field_definition->getSetting('case_sensitive'),
         ),
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UuidItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UuidItem.php
index 84d1ec5..1bdd10e 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UuidItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UuidItem.php
@@ -30,6 +30,7 @@ class UuidItem extends StringItem {
   public static function defaultStorageSettings() {
     return array(
       'max_length' => 128,
+      'is_ascii' => TRUE,
     ) + parent::defaultStorageSettings();
   }
 
diff --git a/core/lib/Drupal/Core/Menu/MenuTreeStorage.php b/core/lib/Drupal/Core/Menu/MenuTreeStorage.php
index 2ce68f7..659d6be 100644
--- a/core/lib/Drupal/Core/Menu/MenuTreeStorage.php
+++ b/core/lib/Drupal/Core/Menu/MenuTreeStorage.php
@@ -1193,7 +1193,7 @@ protected static function schemaDefinition() {
       'fields' => array(
         'menu_name' => array(
           'description' => "The menu name. All links with the same menu name (such as 'tools') are part of the same menu.",
-          'type' => 'varchar',
+          'type' => 'varchar_ascii',
           'length' => 32,
           'not null' => TRUE,
           'default' => '',
@@ -1206,20 +1206,20 @@ protected static function schemaDefinition() {
         ),
         'id' => array(
           'description' => 'Unique machine name: the plugin ID.',
-          'type' => 'varchar',
+          'type' => 'varchar_ascii',
           'length' => 255,
           'not null' => TRUE,
         ),
         'parent' => array(
           'description' => 'The plugin ID for the parent of this link.',
-          'type' => 'varchar',
+          'type' => 'varchar_ascii',
           'length' => 255,
           'not null' => TRUE,
           'default' => '',
         ),
         'route_name' => array(
           'description' => 'The machine name of a defined Symfony Route this menu item represents.',
-          'type' => 'varchar',
+          'type' => 'varchar_ascii',
           'length' => 255,
         ),
         'route_param_key' => array(
@@ -1281,7 +1281,7 @@ protected static function schemaDefinition() {
         ),
         'provider' => array(
           'description' => 'The name of the module that generated this link.',
-          'type' => 'varchar',
+          'type' => 'varchar_ascii',
           'length' => DRUPAL_EXTENSION_NAME_MAX_LENGTH,
           'not null' => TRUE,
           'default' => 'system',
diff --git a/core/modules/aggregator/src/Entity/Feed.php b/core/modules/aggregator/src/Entity/Feed.php
index 6f3d2e2..a5ed081 100644
--- a/core/modules/aggregator/src/Entity/Feed.php
+++ b/core/modules/aggregator/src/Entity/Feed.php
@@ -226,6 +226,7 @@ public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
 
     $fields['hash'] = BaseFieldDefinition::create('string')
       ->setLabel(t('Hash'))
+      ->setSetting('is_ascii', TRUE)
       ->setDescription(t('Calculated hash of the feed data, used for validating cache.'));
 
     $fields['etag'] = BaseFieldDefinition::create('string')
diff --git a/core/modules/aggregator/src/FeedInterface.php b/core/modules/aggregator/src/FeedInterface.php
index 29c6782..e678c90 100644
--- a/core/modules/aggregator/src/FeedInterface.php
+++ b/core/modules/aggregator/src/FeedInterface.php
@@ -170,7 +170,8 @@ public function getHash();
    * Sets the calculated hash of the feed data, used for validating cache.
    *
    * @param string $hash
-   *   A string containing the calculated hash of the feed.
+   *   A string containing the calculated hash of the feed. Must contain
+   *   US ASCII characters only.
    *
    * @return \Drupal\aggregator\FeedInterface
    *   The class instance that this method is called on.
diff --git a/core/modules/ban/ban.install b/core/modules/ban/ban.install
index 7a5494f..b2ea1fe 100644
--- a/core/modules/ban/ban.install
+++ b/core/modules/ban/ban.install
@@ -20,7 +20,7 @@ function ban_schema() {
       ),
       'ip' => array(
         'description' => 'IP address',
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 40,
         'not null' => TRUE,
         'default' => '',
diff --git a/core/modules/comment/comment.install b/core/modules/comment/comment.install
index 64aa6bd..66ab638 100644
--- a/core/modules/comment/comment.install
+++ b/core/modules/comment/comment.install
@@ -46,17 +46,18 @@ function comment_schema() {
         'description' => 'The entity_id of the entity for which the statistics are compiled.',
       ),
       'entity_type' => array(
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'not null' => TRUE,
         'default' => 'node',
         'length' => EntityTypeInterface::ID_MAX_LENGTH,
         'description' => 'The entity_type of the entity to which this comment is a reply.',
       ),
       'field_name' => array(
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'not null' => TRUE,
         'default' => '',
         'length' => FieldStorageConfig::NAME_MAX_LENGTH,
+        'is_ascii' => TRUE,
         'description' => 'The field_name of the field that was used to add this comment.',
       ),
       'cid' => array(
diff --git a/core/modules/comment/src/Entity/Comment.php b/core/modules/comment/src/Entity/Comment.php
index 798a69f..f83f54b 100644
--- a/core/modules/comment/src/Entity/Comment.php
+++ b/core/modules/comment/src/Entity/Comment.php
@@ -303,6 +303,7 @@ public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
     $fields['entity_type'] = BaseFieldDefinition::create('string')
       ->setLabel(t('Entity type'))
       ->setDescription(t('The entity type to which this comment is attached.'))
+      ->setSetting('is_ascii', TRUE)
       ->setSetting('max_length', EntityTypeInterface::ID_MAX_LENGTH);
 
     $fields['comment_type'] = BaseFieldDefinition::create('entity_reference')
@@ -313,6 +314,7 @@ public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
     $fields['field_name'] = BaseFieldDefinition::create('string')
       ->setLabel(t('Comment field name'))
       ->setDescription(t('The field name through which this comment was added.'))
+      ->setSetting('is_ascii', TRUE)
       ->setSetting('max_length', FieldStorageConfig::NAME_MAX_LENGTH);
 
     return $fields;
diff --git a/core/modules/dblog/dblog.install b/core/modules/dblog/dblog.install
index b7454c1..1119c47 100644
--- a/core/modules/dblog/dblog.install
+++ b/core/modules/dblog/dblog.install
@@ -25,7 +25,7 @@ function dblog_schema() {
         'description' => 'The {users}.uid of the user who triggered the event.',
       ),
       'type' => array(
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 64,
         'not null' => TRUE,
         'default' => '',
@@ -69,7 +69,7 @@ function dblog_schema() {
         'description' => 'URL of referring page.',
       ),
       'hostname' => array(
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 128,
         'not null' => TRUE,
         'default' => '',
diff --git a/core/modules/file/file.install b/core/modules/file/file.install
index 6e188c6..fd3503c 100644
--- a/core/modules/file/file.install
+++ b/core/modules/file/file.install
@@ -20,21 +20,21 @@ function file_schema() {
       ),
       'module' => array(
         'description' => 'The name of the module that is using the file.',
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => DRUPAL_EXTENSION_NAME_MAX_LENGTH,
         'not null' => TRUE,
         'default' => '',
       ),
       'type' => array(
         'description' => 'The name of the object type in which the file is used.',
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 64,
         'not null' => TRUE,
         'default' => '',
       ),
       'id' => array(
         'description' => 'The primary key of the object using the file.',
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 64,
         'not null' => TRUE,
         'default' => 0,
diff --git a/core/modules/file/src/Entity/File.php b/core/modules/file/src/Entity/File.php
index 42de0ae..ff38ab3 100644
--- a/core/modules/file/src/Entity/File.php
+++ b/core/modules/file/src/Entity/File.php
@@ -254,6 +254,7 @@ public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
 
     $fields['filemime'] = BaseFieldDefinition::create('string')
       ->setLabel(t('File MIME type'))
+      ->setSetting('is_ascii', TRUE)
       ->setDescription(t("The file's MIME type."));
 
     $fields['filesize'] = BaseFieldDefinition::create('integer')
diff --git a/core/modules/locale/locale.install b/core/modules/locale/locale.install
index 81aadf5..0258767 100644
--- a/core/modules/locale/locale.install
+++ b/core/modules/locale/locale.install
@@ -67,14 +67,14 @@ function locale_schema() {
         'description' => 'The original string in English.',
       ),
       'context' => array(
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 255,
         'not null' => TRUE,
         'default' => '',
         'description' => 'The context this string applies to.',
       ),
       'version' => array(
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 20,
         'not null' => TRUE,
         'default' => 'none',
@@ -103,7 +103,7 @@ function locale_schema() {
         'description' => 'Translation string value in this language.',
       ),
       'language' => array(
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 12,
         'not null' => TRUE,
         'default' => '',
@@ -142,7 +142,7 @@ function locale_schema() {
         'description' => 'Unique identifier of this string.',
       ),
       'type' => array(
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 50,
         'not null' => TRUE,
         'default' => '',
@@ -156,7 +156,7 @@ function locale_schema() {
         'description' => 'Type dependent location information (file name, path, etc).',
       ),
       'version' => array(
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 20,
         'not null' => TRUE,
         'default' => 'none',
@@ -180,14 +180,14 @@ function locale_schema() {
     'description' => 'File import status information for interface translation files.',
     'fields' => array(
       'project' => array(
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => '255',
         'not null' => TRUE,
         'default' => '',
         'description' => 'A unique short name to identify the project the file belongs to.',
       ),
       'langcode' => array(
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => '12',
         'not null' => TRUE,
         'default' => '',
diff --git a/core/modules/menu_link_content/src/Entity/MenuLinkContent.php b/core/modules/menu_link_content/src/Entity/MenuLinkContent.php
index 5570a2a..d6610a0 100644
--- a/core/modules/menu_link_content/src/Entity/MenuLinkContent.php
+++ b/core/modules/menu_link_content/src/Entity/MenuLinkContent.php
@@ -250,6 +250,7 @@ public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
       ->setLabel(t('Bundle'))
       ->setDescription(t('The content menu link bundle.'))
       ->setSetting('max_length', EntityTypeInterface::BUNDLE_MAX_LENGTH)
+      ->setSetting('is_ascii', TRUE)
       ->setReadOnly(TRUE);
 
     $fields['title'] = BaseFieldDefinition::create('string')
@@ -291,7 +292,8 @@ public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
     $fields['menu_name'] = BaseFieldDefinition::create('string')
       ->setLabel(t('Menu name'))
       ->setDescription(t('The menu name. All links with the same menu name (such as "tools") are part of the same menu.'))
-      ->setDefaultValue('tools');
+      ->setDefaultValue('tools')
+      ->setSetting('is_ascii', TRUE);
 
     $fields['link'] = BaseFieldDefinition::create('link')
       ->setLabel(t('Link'))
diff --git a/core/modules/node/node.install b/core/modules/node/node.install
index fa0d245..a7cb55e 100644
--- a/core/modules/node/node.install
+++ b/core/modules/node/node.install
@@ -54,7 +54,7 @@ function node_schema() {
       ),
       'langcode' => array(
         'description' => 'The {language}.langcode of this node.',
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 12,
         'not null' => TRUE,
         'default' => '',
@@ -75,7 +75,7 @@ function node_schema() {
       ),
       'realm' => array(
         'description' => 'The realm in which the user must possess the grant ID. Each node access node can define one or more realms.',
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 255,
         'not null' => TRUE,
         'default' => '',
diff --git a/core/modules/search/search.install b/core/modules/search/search.install
index a298f2f..f920aa5 100644
--- a/core/modules/search/search.install
+++ b/core/modules/search/search.install
@@ -20,14 +20,14 @@ function search_schema() {
         'description' => 'Search item ID, e.g. node ID for nodes.',
       ),
       'langcode' => array(
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => '12',
         'not null' => TRUE,
         'description' => 'The {languages}.langcode of the item variant.',
         'default' => '',
       ),
       'type' => array(
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 64,
         'not null' => TRUE,
         'description' => 'Type of item, e.g. node.',
@@ -67,14 +67,14 @@ function search_schema() {
         'description' => 'The {search_dataset}.sid of the searchable item to which the word belongs.',
       ),
       'langcode' => array(
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => '12',
         'not null' => TRUE,
         'description' => 'The {languages}.langcode of the item variant.',
         'default' => '',
       ),
       'type' => array(
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 64,
         'not null' => TRUE,
         'description' => 'The {search_dataset}.type of the searchable item to which the word belongs.',
diff --git a/core/modules/shortcut/shortcut.install b/core/modules/shortcut/shortcut.install
index c1a6883..2a90306 100644
--- a/core/modules/shortcut/shortcut.install
+++ b/core/modules/shortcut/shortcut.install
@@ -20,7 +20,7 @@ function shortcut_schema() {
         'description' => 'The {users}.uid for this set.',
       ),
       'set_name' => array(
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 32,
         'not null' => TRUE,
         'default' => '',
diff --git a/core/modules/simpletest/simpletest.install b/core/modules/simpletest/simpletest.install
index 47c0ee2..b4792ea 100644
--- a/core/modules/simpletest/simpletest.install
+++ b/core/modules/simpletest/simpletest.install
@@ -108,7 +108,7 @@ function simpletest_schema() {
         'description' => 'Test ID, messages belonging to the same ID are reported together',
       ),
       'test_class' => array(
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 255,
         'not null' => TRUE,
         'default' => '',
@@ -127,14 +127,14 @@ function simpletest_schema() {
         'description' => 'The message itself.',
       ),
       'message_group' => array(
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 255,
         'not null' => TRUE,
         'default' => '',
         'description' => 'The message group this message belongs to. For example: warning, browser, user.',
       ),
       'function' => array(
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 255,
         'not null' => TRUE,
         'default' => '',
diff --git a/core/modules/system/database.api.php b/core/modules/system/database.api.php
index a01ff59..f3d7fe2 100644
--- a/core/modules/system/database.api.php
+++ b/core/modules/system/database.api.php
@@ -256,6 +256,8 @@
  *       'float', 'numeric', or 'serial'. Most types just map to the according
  *       database engine specific datatypes. Use 'serial' for auto incrementing
  *       fields. This will expand to 'INT auto_increment' on MySQL.
+ *       A special 'varchar_ascii' type is also available for limiting machine
+ *       name field to US ASCII characters.
  *     - 'mysql_type', 'pgsql_type', 'sqlite_type', etc.: If you need to
  *       use a record type not included in the officially supported list
  *       of types above, you can specify a type for each database
diff --git a/core/modules/system/src/Tests/Database/SchemaTest.php b/core/modules/system/src/Tests/Database/SchemaTest.php
index a59b9d9..188cfbf 100644
--- a/core/modules/system/src/Tests/Database/SchemaTest.php
+++ b/core/modules/system/src/Tests/Database/SchemaTest.php
@@ -49,6 +49,11 @@ function testSchema() {
           'default' => "'\"funky default'\"",
           'description' => 'Schema column description for string.',
         ),
+        'test_field_string_ascii'  => array(
+          'type' => 'varchar_ascii',
+          'length' => 255,
+          'description' => 'Schema column description for ASCII string.',
+        ),
       ),
     );
     db_create_table('test_table', $table_specification);
@@ -62,6 +67,17 @@ function testSchema() {
     // Assert that the column comment has been set.
     $this->checkSchemaComment($table_specification['fields']['test_field']['description'], 'test_table', 'test_field');
 
+    // Make sure that varchar fields have the correct collation.
+    $columns = db_query('SHOW FULL COLUMNS FROM {test_table}');
+    foreach ($columns as $column) {
+      if ($column->Field == 'test_field_string') {
+        $this->assertTrue($column->Collation == 'utf8_general_ci');
+      }
+      if ($column->Field == 'test_field_string_ascii') {
+        $this->assertTrue($column->Collation == 'ascii_general_ci');
+      }
+    }
+
     // An insert without a value for the column 'test_table' should fail.
     $this->assertFalse($this->tryInsert(), 'Insert without a default failed.');
 
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index f1e6612..b9d221f 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -685,7 +685,7 @@ function system_schema() {
       ),
       'token' => array(
         'description' => "A string token generated against the current user's session id and the batch id, used to ensure that only the user who submitted the batch can effectively access it.",
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 64,
         'not null' => TRUE,
       ),
@@ -717,14 +717,14 @@ function system_schema() {
       ),
       'event' => array(
         'description' => 'Name of event (e.g. contact).',
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 64,
         'not null' => TRUE,
         'default' => '',
       ),
       'identifier' => array(
         'description' => 'Identifier of the visitor, such as an IP address or hostname.',
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 128,
         'not null' => TRUE,
         'default' => '',
@@ -754,14 +754,13 @@ function system_schema() {
     'fields' => array(
       'collection' => array(
         'description' => 'A named collection of key and value pairs.',
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 128,
         'not null' => TRUE,
         'default' => '',
       ),
       'name' => array(
         'description' => 'The key of the key-value pair. As KEY is a SQL reserved keyword, name was chosen instead.',
-        'type' => 'varchar',
         'length' => 128,
         'not null' => TRUE,
         'default' => '',
@@ -781,7 +780,7 @@ function system_schema() {
     'fields' => array(
       'collection' => array(
         'description' => 'A named collection of key and value pairs.',
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 128,
         'not null' => TRUE,
         'default' => '',
@@ -789,7 +788,7 @@ function system_schema() {
       'name' => array(
         // KEY is an SQL reserved word, so use 'name' as the key's field name.
         'description' => 'The key of the key/value pair.',
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 128,
         'not null' => TRUE,
         'default' => '',
@@ -824,7 +823,7 @@ function system_schema() {
         'description' => 'Primary Key: Unique item ID.',
       ),
       'name' => array(
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 255,
         'not null' => TRUE,
         'default' => '',
@@ -862,7 +861,7 @@ function system_schema() {
     'fields' => array(
       'name' => array(
         'description' => 'Primary Key: Machine name of this route',
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 255,
         'not null' => TRUE,
         'default' => '',
@@ -911,14 +910,14 @@ function system_schema() {
     'fields' => array(
       'name' => array(
         'description' => 'Primary Key: Unique name.',
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 255,
         'not null' => TRUE,
         'default' => ''
       ),
       'value' => array(
         'description' => 'A value for the semaphore.',
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 255,
         'not null' => TRUE,
         'default' => ''
@@ -961,13 +960,13 @@ function system_schema() {
       ),
       'sid' => array(
         'description' => "A session ID (hashed). The value is generated by Drupal's session handlers.",
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 128,
         'not null' => TRUE,
       ),
       'hostname' => array(
         'description' => 'The IP address that last used this session ID (sid).',
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 128,
         'not null' => TRUE,
         'default' => '',
@@ -1025,7 +1024,7 @@ function system_schema() {
       ),
       'langcode' => array(
         'description' => "The language code this alias is for; if 'und', the alias will be used for unknown languages. Each Drupal path can have an alias for each supported language.",
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 12,
         'not null' => TRUE,
         'default' => '',
diff --git a/core/modules/text/src/Plugin/Field/FieldType/TextLongItem.php b/core/modules/text/src/Plugin/Field/FieldType/TextLongItem.php
index c55953c..9a24194 100644
--- a/core/modules/text/src/Plugin/Field/FieldType/TextLongItem.php
+++ b/core/modules/text/src/Plugin/Field/FieldType/TextLongItem.php
@@ -34,7 +34,7 @@ public static function schema(FieldStorageDefinitionInterface $field_definition)
           'size' => 'big',
         ),
         'format' => array(
-          'type' => 'varchar',
+          'type' => 'varchar_ascii',
           'length' => 255,
         ),
       ),
diff --git a/core/modules/text/src/Plugin/Field/FieldType/TextWithSummaryItem.php b/core/modules/text/src/Plugin/Field/FieldType/TextWithSummaryItem.php
index 48d4dac..413ad47 100644
--- a/core/modules/text/src/Plugin/Field/FieldType/TextWithSummaryItem.php
+++ b/core/modules/text/src/Plugin/Field/FieldType/TextWithSummaryItem.php
@@ -68,7 +68,7 @@ public static function schema(FieldStorageDefinitionInterface $field_definition)
           'size' => 'big',
         ),
         'format' => array(
-          'type' => 'varchar',
+          'type' => 'varchar_ascii',
           'length' => 255,
         ),
       ),
diff --git a/core/modules/user/user.install b/core/modules/user/user.install
index 7b3c3d3..dd55b49 100644
--- a/core/modules/user/user.install
+++ b/core/modules/user/user.install
@@ -21,14 +21,14 @@ function user_schema() {
       ),
       'module' => array(
         'description' => 'The name of the module declaring the variable.',
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => DRUPAL_EXTENSION_NAME_MAX_LENGTH,
         'not null' => TRUE,
         'default' => '',
       ),
       'name' => array(
         'description' => 'The identifier of the data.',
-        'type' => 'varchar',
+        'type' => 'varchar_ascii',
         'length' => 128,
         'not null' => TRUE,
         'default' => '',
diff --git a/core/tests/Drupal/Tests/Core/Entity/Sql/SqlContentEntityStorageSchemaTest.php b/core/tests/Drupal/Tests/Core/Entity/Sql/SqlContentEntityStorageSchemaTest.php
index 08f73cb..e67b8e6 100644
--- a/core/tests/Drupal/Tests/Core/Entity/Sql/SqlContentEntityStorageSchemaTest.php
+++ b/core/tests/Drupal/Tests/Core/Entity/Sql/SqlContentEntityStorageSchemaTest.php
@@ -802,7 +802,7 @@ public function testDedicatedTableSchema() {
         'description' => "Data storage for $entity_type_id field $field_name.",
         'fields' => array(
           'bundle' => array(
-            'type' => 'varchar',
+            'type' => 'varchar_ascii',
             'length' => 128,
             'not null' => true,
             'default' => '',
@@ -828,7 +828,7 @@ public function testDedicatedTableSchema() {
             'description' => 'The entity revision id this data is attached to, which for an unversioned entity type is the same as the entity id',
           ),
           'langcode' => array(
-            'type' => 'varchar',
+            'type' => 'varchar_ascii',
             'length' => 32,
             'not null' => true,
             'default' => '',
@@ -947,7 +947,7 @@ public function testDedicatedTableSchemaForEntityWithStringIdentifier() {
         'description' => "Data storage for $entity_type_id field $field_name.",
         'fields' => array(
           'bundle' => array(
-            'type' => 'varchar',
+            'type' => 'varchar_ascii',
             'length' => 128,
             'not null' => true,
             'default' => '',
@@ -961,19 +961,19 @@ public function testDedicatedTableSchemaForEntityWithStringIdentifier() {
             'description' => 'A boolean indicating whether this data item has been deleted',
           ),
           'entity_id' => array(
-            'type' => 'varchar',
+            'type' => 'varchar_ascii',
             'length' => 128,
             'not null' => true,
             'description' => 'The entity id this data is attached to',
           ),
           'revision_id' => array(
-            'type' => 'varchar',
+            'type' => 'varchar_ascii',
             'length' => 128,
             'not null' => true,
             'description' => 'The entity revision id this data is attached to, which for an unversioned entity type is the same as the entity id',
           ),
           'langcode' => array(
-            'type' => 'varchar',
+            'type' => 'varchar_ascii',
             'length' => 32,
             'not null' => true,
             'default' => '',