diff --git a/core/includes/file.inc b/core/includes/file.inc
index a963e71a59..ea71ec727f 100644
--- a/core/includes/file.inc
+++ b/core/includes/file.inc
@@ -474,19 +474,91 @@ function file_unmanaged_copy($source, $destination = NULL, $replace = FILE_EXIST
  * Internal function that prepares the destination for a file_unmanaged_copy or
  * file_unmanaged_move operation.
  *
+ * - Checks if $source and $destination are valid and readable/writable.
+ * - Checks that $source is not equal to $destination; if they are an error
+ *   is reported.
+ * - If file already exists in $destination either the call will error out,
+ *   replace the file or rename the file based on the $replace parameter.
+ *
+ * @param $source
+ *   A string specifying the filepath or URI of the source file.
+ * @param $destination
+ *   A URI containing the destination that $source should be moved/copied to.
+ *   The URI may be a bare filepath (without a scheme) and in that case the
+ *   default scheme (file://) will be used. If this value is omitted, Drupal's
+ *   default files scheme will be used, usually "public://".
+ * @param $replace
+ *   Replace behavior when the destination file already exists:
+ *   - FILE_EXISTS_REPLACE - Replace the existing file.
+ *   - FILE_EXISTS_RENAME - Append _{incrementing number} until the filename is
+ *       unique.
+ *   - FILE_EXISTS_ERROR - Do nothing and return FALSE.
+ *
  * @deprecated in Drupal 8.7.0, will be removed before Drupal 9.0.0.
- *   Use \Drupal\Core\File\UnmanagedFileHandler::prepareDestination() instead.
+ *   Use \Drupal\Core\File\FileSystemInterface::getDestinationFilename() instead.
  *
  * @see https://www.drupal.org/node/3006851
  */
 function file_unmanaged_prepare($source, &$destination = NULL, $replace = FILE_EXISTS_RENAME) {
-  @trigger_error('file_unmanaged_prepare() is deprecated in Drupal 8.7.0 and will be removed before Drupal 9.0.0. Use \Drupal\Core\File\UnmanagedFileHandler::prepareDestination(). See https://www.drupal.org/node/3006851.', E_USER_DEPRECATED);
-  try {
-    \Drupal::service('file_system')->prepareDestination($source, $destination, $replace);
+  @trigger_error('file_unmanaged_prepare() is deprecated in Drupal 8.7.0 and will be removed before Drupal 9.0.0. Use \Drupal\Core\File\FileSystemInterface::getDestinationFilename() instead. See https://www.drupal.org/node/3006851.', E_USER_DEPRECATED);
+  $logger = \Drupal::logger('file');
+  /** @var \Drupal\Core\File\FileSystemInterface $file_system */
+  $file_system = \Drupal::service('file_system');
+
+  // Assert that the source file actually exists.
+  if (!file_exists($source)) {
+    // @todo Replace \Drupal::messenger()->addError() calls with exceptions
+    // instead.
+    \Drupal::messenger()->addError(t('The specified file %file could not be moved/copied because no file by that name exists. Please check that you supplied the correct filename.', ['%file' => $original_source]));
+    if (($realpath = $file_system->realpath($original_source)) !== FALSE) {
+      $logger->notice('File %file (%realpath) could not be moved/copied because it does not exist.', ['%file' => $original_source, '%realpath' => $realpath]);
+    }
+    else {
+      $logger->notice('File %file could not be moved/copied because it does not exist.', ['%file' => $original_source]);
+    }
+    return FALSE;
   }
-  catch (FileException $e) {
+
+  // Build a destination URI if necessary.
+  if (!isset($destination)) {
+    $destination = file_build_uri(drupal_basename($source));
+  }
+
+  // Prepare the destination directory.
+  if (file_prepare_directory($destination)) {
+    // The destination is already a directory, so append the source basename.
+    $destination = file_stream_wrapper_uri_normalize($destination . '/' . drupal_basename($source));
+  }
+  else {
+    // Perhaps $destination is a dir/file?
+    $dirname = drupal_dirname($destination);
+    if (!file_prepare_directory($dirname)) {
+      // The destination is not valid.
+      $logger->notice('File %file could not be moved/copied because the destination directory %destination is not configured correctly.', ['%file' => $original_source, '%destination' => $dirname]);
+      \Drupal::messenger()->addError(t('The specified file %file could not be moved/copied because the destination directory is not properly configured. This may be caused by a problem with file or directory permissions. More information is available in the system log.', ['%file' => $original_source]));
+      return FALSE;
+    }
+  }
+
+  // Determine whether we can perform this operation based on overwrite rules.
+  $destination = file_destination($destination, $replace);
+  if ($destination === FALSE) {
+    \Drupal::messenger()->addError(t('The file %file could not be moved/copied because a file by that name already exists in the destination directory.', ['%file' => $original_source]));
+    $logger->notice('File %file could not be moved/copied because a file by that name already exists in the destination directory (%destination)', ['%file' => $original_source, '%destination' => $destination]);
     return FALSE;
   }
+
+  // Assert that the source and destination filenames are not the same.
+  $real_source = $file_system->realpath($source);
+  $real_destination = $file_system->realpath($destination);
+  if ($source == $destination || ($real_source !== FALSE) && ($real_source == $real_destination)) {
+    \Drupal::messenger()->addError(t('The specified file %file was not moved/copied because it would overwrite itself.', ['%file' => $source]));
+    $logger->notice('File %file could not be moved/copied because it would overwrite itself.', ['%file' => $source]);
+    return FALSE;
+  }
+  // Make sure the .htaccess files are present.
+  file_ensure_htaccess();
+  return TRUE;
 }
 
 /**
diff --git a/core/lib/Drupal/Core/File/FileSystem.php b/core/lib/Drupal/Core/File/FileSystem.php
index 36b65f6d5d..a9b7457508 100644
--- a/core/lib/Drupal/Core/File/FileSystem.php
+++ b/core/lib/Drupal/Core/File/FileSystem.php
@@ -311,7 +311,7 @@ public function validScheme($scheme) {
    * {@inheritdoc}
    */
   public function copy($source, $destination = NULL, $replace = self::EXISTS_RENAME) {
-    $this->doPrepareDestination($source, $destination, $replace);
+    $this->prepareDestination($source, $destination, $replace);
 
     // Perform the copy operation.
     if (!@copy($source, $destination)) {
@@ -324,7 +324,7 @@ public function copy($source, $destination = NULL, $replace = self::EXISTS_RENAM
           '%source' => $source,
           '%destination' => $destination,
         ]);
-        throw new FileWriteException(sprintf("The specified file '%s' could not be copied to '%s'.", $source, $destination));
+        throw new FileWriteException("The specified file '$source' could not be copied to '$destination'.");
       }
     }
 
@@ -341,14 +341,14 @@ public function delete($path) {
     if (is_file($path)) {
       if (!$this->unlink($path)) {
         $this->logger->error("Failed to unlink file '%path'.", ['%path' => $path]);
-        throw new FileException(sprintf("Failed to unlink file '%s'.", $path));
+        throw new FileException("Failed to unlink file '$path'.");
       }
       return TRUE;
     }
 
     if (is_dir($path)) {
       $this->logger->error("Cannot delete '%path' because it is a directory. Use deleteRecursive() instead.", ['%path' => $path]);
-      throw new NotRegularFileException(sprintf("Cannot delete '%s' because it is a directory. Use deleteRecursive() instead.", $path));
+      throw new NotRegularFileException("Cannot delete '$path' because it is a directory. Use deleteRecursive() instead.");
     }
 
     // Do not throw exception for non-existent file, but return FALSE to
@@ -361,7 +361,7 @@ public function delete($path) {
     // We cannot handle anything other than files and directories.
     // Throw an exception for everything else (sockets, symbolic links, etc).
     $this->logger->error("The file '%path' is not of a recognized type so it was not deleted.", ['%path' => $path]);
-    throw new NotRegularFileException(sprintf("The file '%s' is not of a recognized type so it was not deleted.", $path));
+    throw new NotRegularFileException("The file '$path' is not of a recognized type so it was not deleted.");
   }
 
   /**
@@ -393,7 +393,7 @@ public function deleteRecursive($path, callable $callback = NULL) {
    * {@inheritdoc}
    */
   public function move($source, $destination = NULL, $replace = self::EXISTS_RENAME) {
-    $this->doPrepareDestination($source, $destination, $replace);
+    $this->prepareDestination($source, $destination, $replace);
 
     // Ensure compatibility with Windows.
     // @see \Drupal\Core\File\FileSystemInterface::unlink().
@@ -417,14 +417,14 @@ public function move($source, $destination = NULL, $replace = self::EXISTS_RENAM
           '%source' => $source,
           '%destination' => $destination,
         ]);
-        throw new FileWriteException(sprintf("The specified file '%s' could not be moved to '%s'.", $source, $destination));
+        throw new FileWriteException("The specified file '$source' could not be moved to '$destination'.");
       }
       if (!@unlink($real_source)) {
         $this->logger->error("The source file '%source' could not be unlinked after copying to '%destination'.", [
           '%source' => $source,
           '%destination' => $destination,
         ]);
-        throw new FileException(sprintf("The source file '%s' could not be unlinked after copying to '%s'.", $source, $destination));
+        throw new FileException("The source file '$source' could not be unlinked after copying to '$destination'.");
       }
     }
 
@@ -457,44 +457,10 @@ public function move($source, $destination = NULL, $replace = self::EXISTS_RENAM
    *     is unique.
    *   - FILE_EXISTS_ERROR - Do nothing and return FALSE.
    *
-   * @deprecated This public method is deprecated in 8.7.0 and will be converted
-   *   into a protected method before 9.0.0.
-   *
-   * @see \Drupal\Core\File\UnmanagedFileHandler::copy()
-   * @see \Drupal\Core\File\UnmanagedFileHandler::move()
-   */
-  public function prepareDestination($source, &$destination = NULL, $replace = self::EXISTS_RENAME) {
-    @trigger_error('FileSystem::prepareDestination() is deprecated in Drupal 8.7.0 and will be converted to a protected method before Drupal 9.0.0. See https://www.drupal.org/node/3006851.', E_USER_DEPRECATED);
-    $this->doPrepareDestination($source, $destination, $replace);
-  }
-
-  /**
-   * Prepares the destination for a file copy or move operation.
-   *
-   * - Checks if $source and $destination are valid and readable/writable.
-   * - Checks that $source is not equal to $destination; if they are an error
-   *   is reported.
-   * - If file already exists in $destination either the call will error out,
-   *   replace the file or rename the file based on the $replace parameter.
-   *
-   * @param string $source
-   *   A string specifying the filepath or URI of the source file.
-   * @param string|null $destination
-   *   A URI containing the destination that $source should be moved/copied to.
-   *   The URI may be a bare filepath (without a scheme) and in that case the
-   *   default scheme (file://) will be used. If this value is omitted, Drupal's
-   *   default files scheme will be used, usually "public://".
-   * @param int $replace
-   *   Replace behavior when the destination file already exists:
-   *   - FILE_EXISTS_REPLACE - Replace the existing file.
-   *   - FILE_EXISTS_RENAME - Append _{incrementing number} until the filename
-   *     is unique.
-   *   - FILE_EXISTS_ERROR - Do nothing and return FALSE.
-   *
-   * @see \Drupal\Core\File\UnmanagedFileHandler::copy()
-   * @see \Drupal\Core\File\UnmanagedFileHandler::move()
+   * @see \Drupal\Core\File\FileSystemInterface::copy()
+   * @see \Drupal\Core\File\FileSystemInterface::move()
    */
-  protected function doPrepareDestination($source, &$destination = NULL, $replace = self::EXISTS_RENAME) {
+  protected function prepareDestination($source, &$destination = NULL, $replace = self::EXISTS_RENAME) {
     $original_source = $source;
 
     // Assert that the source file actually exists.
@@ -504,13 +470,13 @@ protected function doPrepareDestination($source, &$destination = NULL, $replace
           '%original_source' => $original_source,
           '%realpath' => $realpath,
         ]);
-        throw new FileNotExistsException(sprintf("File '%s' ('%s') could not be copied because it does not exist.", $original_source, $realpath));
+        throw new FileNotExistsException("File '$original_source' ('$realpath') could not be copied because it does not exist.");
       }
       else {
         $this->logger->error("File '%original_source' could not be copied because it does not exist.", [
           '%original_source' => $original_source,
         ]);
-        throw new FileNotExistsException(sprintf("File '%s' could not be copied because it does not exist.", $original_source));
+        throw new FileNotExistsException("File '$original_source' could not be copied because it does not exist.");
       }
     }
 
@@ -531,7 +497,7 @@ protected function doPrepareDestination($source, &$destination = NULL, $replace
         $this->logger->error("The specified file '%original_source' could not be copied because the destination directory is not properly configured. This may be caused by a problem with file or directory permissions.", [
           '%original_source' => $original_source,
         ]);
-        throw new DirectoryNotReadyException(sprintf("The specified file '%s' could not be copied because the destination directory is not properly configured. This may be caused by a problem with file or directory permissions.", $original_source));
+        throw new DirectoryNotReadyException("The specified file '$original_source' could not be copied because the destination directory is not properly configured. This may be caused by a problem with file or directory permissions.");
       }
     }
 
@@ -542,7 +508,7 @@ protected function doPrepareDestination($source, &$destination = NULL, $replace
         '%original_source' => $original_source,
         '%destination' => $destination,
       ]);
-      throw new FileExistsException(sprintf("File '%s' could not be copied because a file by that name already exists in the destination directory ('%s').", $original_source, $destination));
+      throw new FileExistsException("File '$original_source' could not be copied because a file by that name already exists in the destination directory ('$destination').");
     }
 
     // Assert that the source and destination filenames are not the same.
@@ -552,7 +518,7 @@ protected function doPrepareDestination($source, &$destination = NULL, $replace
       $this->logger->error("File '%source' could not be copied because it would overwrite itself.", [
         '%source' => $source,
       ]);
-      throw new FileException(sprintf("File '%s' could not be copied because it would overwrite itself.", $source));
+      throw new FileException("File '$source' could not be copied because it would overwrite itself.");
     }
     // Make sure the .htaccess files are present.
     // @todo Replace with a service in https://www.drupal.org/project/drupal/issues/2620304.
@@ -567,7 +533,7 @@ public function saveData($data, $destination = NULL, $replace = self::EXISTS_REN
     $temp_name = $this->tempnam('temporary://', 'file');
     if (file_put_contents($temp_name, $data) === FALSE) {
       $this->logger->error("Temporary file '%temp_name' could not be created.", ['%temp_name' => $temp_name]);
-      throw new FileWriteException(sprintf("Temporary file '%s' could not be created.", $temp_name));
+      throw new FileWriteException("Temporary file '$temp_name' could not be created.");
     }
 
     // Move the file to its final destination.
diff --git a/core/tests/Drupal/KernelTests/Core/File/FileSystemDeprecationTest.php b/core/tests/Drupal/KernelTests/Core/File/FileSystemDeprecationTest.php
index 1cd157a9e3..1e434c4246 100644
--- a/core/tests/Drupal/KernelTests/Core/File/FileSystemDeprecationTest.php
+++ b/core/tests/Drupal/KernelTests/Core/File/FileSystemDeprecationTest.php
@@ -55,7 +55,7 @@ public function testDeprecatedUnmanagedFileMove() {
   }
 
   /**
-   * @expectedDeprecation file_unmanaged_prepare() is deprecated in Drupal 8.7.0 and will be removed before Drupal 9.0.0. Use \Drupal\Core\File\UnmanagedFileHandler::prepareDestination(). See https://www.drupal.org/node/3006851.
+   * @expectedDeprecation file_unmanaged_prepare() is deprecated in Drupal 8.7.0 and will be removed before Drupal 9.0.0. Use \Drupal\Core\File\FileSystemInterface::getDestinationFilename() instead. See https://www.drupal.org/node/3006851.
    */
   public function testDeprecatedUnmanagedPrepare() {
     $this->assertNotNull(file_unmanaged_prepare(NULL));