diff --git a/core/modules/hal/config/install/hal.settings.yml b/core/modules/hal/config/install/hal.settings.yml
index 67107af00d..1c895c1718 100644
--- a/core/modules/hal/config/install/hal.settings.yml
+++ b/core/modules/hal/config/install/hal.settings.yml
@@ -1,3 +1,4 @@
 # Set the domain for HAL type and relation links.
 # If left blank, the site's domain will be used.
 link_domain: ~
+bc_file_uri_as_url_normalizer: false
diff --git a/core/modules/hal/config/schema/hal.schema.yml b/core/modules/hal/config/schema/hal.schema.yml
index 3192d67580..b70f47eaff 100644
--- a/core/modules/hal/config/schema/hal.schema.yml
+++ b/core/modules/hal/config/schema/hal.schema.yml
@@ -6,3 +6,6 @@ hal.settings:
     link_domain:
       type: string
       label: 'Domain of the relation'
+    bc_file_uri_as_url_normalizer:
+      type: boolean
+      label: 'Whether to retain pre Drupal 8.5 behavior of normalizing file URI values as a full URL.'
diff --git a/core/modules/hal/hal.install b/core/modules/hal/hal.install
index 78810e37f5..77e932f74f 100644
--- a/core/modules/hal/hal.install
+++ b/core/modules/hal/hal.install
@@ -31,3 +31,15 @@ function hal_update_8301() {
   $hal_settings->set('link_domain', $link_domain);
   $hal_settings->save(TRUE);
 }
+
+/**
+ * Add hal.settings::bc_file_uri_as_url_normalizer configuration.
+ */
+function hal_update_8501() {
+  $config_factory = \Drupal::configFactory();
+  $config_factory->getEditable('hal.settings')
+    ->set('bc_file_uri_as_url_normalizer', FALSE)
+    ->save(TRUE);
+
+  return t('The REST API will no longer return the full URL for file entity URI values. It will return the URI value itself, with an additional URL property providing a root relative file path. If your site depends on these value being strings, <a href="https://www.drupal.org/node/2925783">read the change record to learn how to enable the BC mode.</a>');
+}
diff --git a/core/modules/hal/hal.services.yml b/core/modules/hal/hal.services.yml
index ca28f522b4..faf3fc101f 100644
--- a/core/modules/hal/hal.services.yml
+++ b/core/modules/hal/hal.services.yml
@@ -12,6 +12,11 @@ services:
     class: Drupal\hal\Normalizer\FieldNormalizer
     tags:
       - { name: normalizer, priority: 10 }
+  serializer.normalizer.file_entity.hal:
+    class: Drupal\hal\Normalizer\FileEntityNormalizer
+    arguments: ['@entity.manager', '@http_client', '@hal.link_manager', '@module_handler', '@config.factory']
+    tags:
+      - { name: normalizer, priority: 20 }
   serializer.normalizer.timestamp_item.hal:
    class: Drupal\hal\Normalizer\TimestampItemNormalizer
    tags:
diff --git a/core/modules/hal/src/Normalizer/FileEntityNormalizer.php b/core/modules/hal/src/Normalizer/FileEntityNormalizer.php
new file mode 100644
index 0000000000..31a0f53f0e
--- /dev/null
+++ b/core/modules/hal/src/Normalizer/FileEntityNormalizer.php
@@ -0,0 +1,84 @@
+<?php
+
+namespace Drupal\hal\Normalizer;
+
+use Drupal\Core\Config\ConfigFactoryInterface;
+use Drupal\Core\Entity\EntityManagerInterface;
+use Drupal\Core\Extension\ModuleHandlerInterface;
+use Drupal\hal\LinkManager\LinkManagerInterface;
+use GuzzleHttp\ClientInterface;
+
+/**
+ * Converts the Drupal entity object structure to a HAL array structure.
+ *
+ * @deprecated in Drupal 8.5.x, to be removed before Drupal 9.0.x.
+ */
+class FileEntityNormalizer extends ContentEntityNormalizer {
+
+  /**
+   * The interface or class that this Normalizer supports.
+   *
+   * @var string
+   */
+  protected $supportedInterfaceOrClass = 'Drupal\file\FileInterface';
+
+  /**
+   * The HTTP client.
+   *
+   * @var \GuzzleHttp\ClientInterface
+   */
+  protected $httpClient;
+
+  /**
+   * The hal config.
+   *
+   * @var \Drupal\Core\Config\Config
+   */
+  protected $config;
+
+  /**
+   * Constructs a FileEntityNormalizer object.
+   *
+   * @param \Drupal\Core\Entity\EntityManagerInterface $entity_manager
+   *   The entity manager.
+   * @param \GuzzleHttp\ClientInterface $http_client
+   *   The HTTP Client.
+   * @param \Drupal\hal\LinkManager\LinkManagerInterface $link_manager
+   *   The hypermedia link manager.
+   * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
+   *   The module handler.
+   */
+  public function __construct(EntityManagerInterface $entity_manager, ClientInterface $http_client, LinkManagerInterface $link_manager, ModuleHandlerInterface $module_handler, ConfigFactoryInterface $config_facotry) {
+    parent::__construct($link_manager, $entity_manager, $module_handler);
+
+    $this->httpClient = $http_client;
+    $this->config = $config_facotry->get('hal.settings');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function normalize($entity, $format = NULL, array $context = []) {
+    $data = parent::normalize($entity, $format, $context);
+
+    if ($this->config->get('bc_file_uri_as_url_normalizer')) {
+      // Replace the file url with a full url for the file.
+      $data['uri'][0]['value'] = $this->getEntityUri($entity);
+    }
+
+    return $data;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function denormalize($data, $class, $format = NULL, array $context = []) {
+    $file_data = (string) $this->httpClient->get($data['uri'][0]['value'])->getBody();
+
+    $path = 'temporary://' . drupal_basename($data['uri'][0]['value']);
+    $data['uri'] = file_unmanaged_save_data($file_data, $path);
+
+    return $this->entityManager->getStorage('file')->create($data);
+  }
+
+}
diff --git a/core/modules/hal/tests/src/Functional/FileDenormalizeTest.php b/core/modules/hal/tests/src/Functional/FileDenormalizeTest.php
new file mode 100644
index 0000000000..dbb708f8ca
--- /dev/null
+++ b/core/modules/hal/tests/src/Functional/FileDenormalizeTest.php
@@ -0,0 +1,86 @@
+<?php
+
+namespace Drupal\Tests\hal\Functional;
+
+use Drupal\file\Entity\File;
+use Drupal\Tests\BrowserTestBase;
+
+/**
+ * Tests that file entities can be denormalized in HAL.
+ *
+ * @group hal
+ * @see \Drupal\hal\Normalizer\FileEntityNormalizer
+ */
+class FileDenormalizeTest extends BrowserTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = ['hal', 'file', 'node'];
+
+  protected function setUp() {
+    parent::setUp();
+
+    // Override the default configuration to the hal BC setting is enabled, to
+    // return the full URL value as the file URI 'value'.
+    \Drupal::configFactory()
+      ->getEditable('hal.settings')
+      ->set('bc_file_uri_as_url_normalizer', TRUE)
+      ->save(TRUE);
+  }
+
+  /**
+   * Tests file entity denormalization.
+   */
+  public function testFileDenormalize() {
+    $file_params = [
+      'filename' => 'test_1.txt',
+      'uri' => 'public://test_1.txt',
+      'filemime' => 'text/plain',
+      'status' => FILE_STATUS_PERMANENT,
+    ];
+    // Create a new file entity.
+    $file = File::create($file_params);
+    file_put_contents($file->getFileUri(), 'hello world');
+    $file->save();
+
+    $serializer = \Drupal::service('serializer');
+    $normalized_data = $serializer->normalize($file, 'hal_json');
+    $denormalized = $serializer->denormalize($normalized_data, 'Drupal\file\Entity\File', 'hal_json');
+
+    $this->assertTrue($denormalized instanceof File, 'A File instance was created.');
+
+    $this->assertIdentical('temporary://' . $file->getFilename(), $denormalized->getFileUri(), 'The expected file URI was found.');
+    $this->assertTrue(file_exists($denormalized->getFileUri()), 'The temporary file was found.');
+
+    $this->assertIdentical($file->uuid(), $denormalized->uuid(), 'The expected UUID was found');
+    $this->assertIdentical($file->getMimeType(), $denormalized->getMimeType(), 'The expected MIME type was found.');
+    $this->assertIdentical($file->getFilename(), $denormalized->getFilename(), 'The expected filename was found.');
+    $this->assertTrue($denormalized->isPermanent(), 'The file has a permanent status.');
+
+    // Try to denormalize with the file uri only.
+    $file_name = 'test_2.txt';
+    $file_path = 'public://' . $file_name;
+
+    file_put_contents($file_path, 'hello world');
+    $file_uri = file_create_url($file_path);
+
+    $data = [
+      'uri' => [
+        ['value' => $file_uri],
+      ],
+    ];
+
+    $denormalized = $serializer->denormalize($data, 'Drupal\file\Entity\File', 'hal_json');
+
+    $this->assertIdentical('temporary://' . $file_name, $denormalized->getFileUri(), 'The expected file URI was found.');
+    $this->assertTrue(file_exists($denormalized->getFileUri()), 'The temporary file was found.');
+
+    $this->assertIdentical('text/plain', $denormalized->getMimeType(), 'The expected MIME type was found.');
+    $this->assertIdentical($file_name, $denormalized->getFilename(), 'The expected filename was found.');
+    $this->assertFalse($denormalized->isPermanent(), 'The file has a permanent status.');
+  }
+
+}