diff --git a/src/wp-admin/includes/admin-filters.php b/src/wp-admin/includes/admin-filters.php
index e80c111dde..f5f9600332 100644
--- a/src/wp-admin/includes/admin-filters.php
+++ b/src/wp-admin/includes/admin-filters.php
@@ -37,6 +37,8 @@ add_filter( 'media_upload_library', 'media_upload_library' );
 
 add_filter( 'media_upload_tabs', 'update_gallery_tab' );
 
+add_filter( 'image_editor_output_format', 'wp_default_image_output_mapping' );
+
 // Admin color schemes.
 add_action( 'admin_init', 'register_admin_color_schemes', 1 );
 add_action( 'admin_head', 'wp_color_scheme_settings' );
diff --git a/src/wp-admin/includes/image-edit.php b/src/wp-admin/includes/image-edit.php
index e814fc47e7..9c71e68794 100644
--- a/src/wp-admin/includes/image-edit.php
+++ b/src/wp-admin/includes/image-edit.php
@@ -917,10 +917,12 @@ function wp_save_image( $post_id ) {
 	}
 
 	// Save the full-size file, also needed to create sub-sizes.
-	if ( ! wp_save_image_file( $new_path, $img, $post->post_mime_type, $post_id ) ) {
+	$saved = wp_save_image_file( $new_path, $img, $post->post_mime_type, $post_id );
+	if ( ! $saved ) {
 		$return->error = esc_js( __( 'Unable to save the image.' ) );
 		return $return;
 	}
+	$new_path = $saved['path'];
 
 	if ( 'nothumb' === $target || 'all' === $target || 'full' === $target || $scaled ) {
 		$tag = false;
diff --git a/src/wp-admin/includes/media.php b/src/wp-admin/includes/media.php
index 510fff563d..e9cea8b6fb 100644
--- a/src/wp-admin/includes/media.php
+++ b/src/wp-admin/includes/media.php
@@ -3843,3 +3843,18 @@ function wp_media_attach_action( $parent_id, $action = 'attach' ) {
 		exit;
 	}
 }
+
+/**
+ * Filters the default image output mapping.
+ *
+ * With this filter callback, WebP image files will be generated for certain JPEG source files.
+ *
+ * @since 6.1.0
+ *
+ * @param array $output_mapping Map of mime type to output format.
+ * @retun array The adjusted default output mapping.
+ */
+function wp_default_image_output_mapping( $output_mapping ) {
+	$output_mapping['image/jpeg'] = 'image/webp';
+	return $output_mapping;
+}
diff --git a/src/wp-includes/class-wp-image-editor.php b/src/wp-includes/class-wp-image-editor.php
index caa3092d36..15e4aa8d6e 100644
--- a/src/wp-includes/class-wp-image-editor.php
+++ b/src/wp-includes/class-wp-image-editor.php
@@ -424,19 +424,26 @@ abstract class WP_Image_Editor {
 		return array( $filename, $new_ext, $mime_type );
 	}
 
-	/**
-	 * Builds an output filename based on current file, and adding proper suffix
+		/**
+	 * Builds an output filename based on current file, and adding proper suffix.
 	 *
 	 * @since 3.5.0
-	 *
-	 * @param string $suffix
-	 * @param string $dest_path
-	 * @param string $extension
-	 * @return string filename
+	 * @since 6.1.0 Skips adding a suffix when set to an empty string. When the
+	 *              file extension being generated doesn't match the image file extension,
+	 *              add the extension to the suffix
+	 *
+	 * @param string $suffix    Optional. Suffix to add to the filename. The default null
+	 *                          will result in a 'widthxheight' suffix. Passing
+	 *                          an empty string will result in no suffix.
+	 * @param string $dest_path Optional. The path to save the file to. The default null
+	 *                          will use the image file path.
+	 * @param string $extension Optional. The file extension to use. The default null
+	 *                          will use the image file extension.
+	 * @return string filename The generated file name.
 	 */
 	public function generate_filename( $suffix = null, $dest_path = null, $extension = null ) {
 		// $suffix will be appended to the destination filename, just before the extension.
-		if ( ! $suffix ) {
+		if ( null === $suffix ) {
 			$suffix = $this->get_suffix();
 		}
 
@@ -457,7 +464,21 @@ abstract class WP_Image_Editor {
 			}
 		}
 
-		return trailingslashit( $dir ) . "{$name}-{$suffix}.{$new_ext}";
+		if ( empty( $suffix ) ) {
+			$suffix = '';
+		} else {
+			$suffix = "-{$suffix}";
+		}
+
+		// When the file extension being generated doesn't match the image file extension,
+		// add the extension to the suffix to ensure a unique file name. Prevents
+		// name conflicts when a single image type can have multiple extensions,
+		// eg. .jpg, .jpeg and .jpe are all valid JPEG extensions.
+		if ( ! empty( $extension ) && $extension !== $ext ) {
+			$suffix .= "-{$ext}";
+		}
+
+		return trailingslashit( $dir ) . "{$name}{$suffix}.{$new_ext}";
 	}
 
 	/**
diff --git a/tests/phpunit/tests/image/editor.php b/tests/phpunit/tests/image/editor.php
index 487dad0664..d478dd6bf1 100644
--- a/tests/phpunit/tests/image/editor.php
+++ b/tests/phpunit/tests/image/editor.php
@@ -18,11 +18,20 @@ class Tests_Image_Editor extends WP_Image_UnitTestCase {
 		require_once ABSPATH . WPINC . '/class-wp-image-editor.php';
 
 		require_once DIR_TESTDATA . '/../includes/mock-image-editor.php';
+		add_filter( 'image_editor_output_format', '__return_empty_array' );
 
 		// This needs to come after the mock image editor class is loaded.
 		parent::set_up();
 	}
 
+	/**
+	 * Tear down the class.
+	 */
+	public function tear_down() {
+		remove_filter( 'image_editor_output_format', '__return_empty_array' );
+		parent::tear_down();
+	}
+
 	/**
 	 * Test wp_get_image_editor() where load returns true
 	 *
@@ -226,10 +235,10 @@ class Tests_Image_Editor extends WP_Image_UnitTestCase {
 		$this->assertSame( trailingslashit( realpath( get_temp_dir() ) ), trailingslashit( realpath( dirname( $editor->generate_filename( null, get_temp_dir() ) ) ) ) );
 
 		// Test with a suffix only.
-		$this->assertSame( 'canola-100x50.png', wp_basename( $editor->generate_filename( null, null, 'png' ) ) );
+		$this->assertSame( 'canola-100x50-jpg.png', wp_basename( $editor->generate_filename( null, null, 'png' ) ) );
 
 		// Combo!
-		$this->assertSame( trailingslashit( realpath( get_temp_dir() ) ) . 'canola-new.png', $editor->generate_filename( 'new', realpath( get_temp_dir() ), 'png' ) );
+		$this->assertSame( trailingslashit( realpath( get_temp_dir() ) ) . 'canola-new-jpg.png', $editor->generate_filename( 'new', realpath( get_temp_dir() ), 'png' ) );
 
 		// Test with a stream destination.
 		$this->assertSame( 'file://testing/path/canola-100x50.jpg', $editor->generate_filename( null, 'file://testing/path' ) );
diff --git a/tests/phpunit/tests/image/editorGd.php b/tests/phpunit/tests/image/editorGd.php
index 5d967bdcdb..88dfb80299 100644
--- a/tests/phpunit/tests/image/editorGd.php
+++ b/tests/phpunit/tests/image/editorGd.php
@@ -17,6 +17,8 @@ class Tests_Image_Editor_GD extends WP_Image_UnitTestCase {
 		require_once ABSPATH . WPINC . '/class-wp-image-editor.php';
 		require_once ABSPATH . WPINC . '/class-wp-image-editor-gd.php';
 
+		add_filter( 'image_editor_output_format', '__return_empty_array' );
+
 		// This needs to come after the mock image editor class is loaded.
 		parent::set_up();
 	}
@@ -30,6 +32,8 @@ class Tests_Image_Editor_GD extends WP_Image_UnitTestCase {
 
 		$this->remove_added_uploads();
 
+		remove_filter( 'image_editor_output_format', '__return_empty_array' );
+
 		parent::tear_down();
 	}
 
diff --git a/tests/phpunit/tests/image/editorImagick.php b/tests/phpunit/tests/image/editorImagick.php
index 02e0590a2e..a6698ec22c 100644
--- a/tests/phpunit/tests/image/editorImagick.php
+++ b/tests/phpunit/tests/image/editorImagick.php
@@ -18,6 +18,8 @@ class Tests_Image_Editor_Imagick extends WP_Image_UnitTestCase {
 		require_once ABSPATH . WPINC . '/class-wp-image-editor-imagick.php';
 		require_once DIR_TESTROOT . '/includes/class-wp-test-stream.php';
 
+		add_filter( 'image_editor_output_format', '__return_empty_array' );
+
 		// This needs to come after the mock image editor class is loaded.
 		parent::set_up();
 	}
@@ -31,6 +33,8 @@ class Tests_Image_Editor_Imagick extends WP_Image_UnitTestCase {
 
 		$this->remove_added_uploads();
 
+		remove_filter( 'image_editor_output_format', '__return_empty_array' );
+
 		parent::tear_down();
 	}
 
diff --git a/tests/phpunit/tests/image/functions.php b/tests/phpunit/tests/image/functions.php
index 86d559145e..75e5514c8b 100644
--- a/tests/phpunit/tests/image/functions.php
+++ b/tests/phpunit/tests/image/functions.php
@@ -25,6 +25,16 @@ class Tests_Image_Functions extends WP_UnitTestCase {
 		foreach ( glob( $folder ) as $file ) {
 			unlink( $file );
 		}
+
+		add_filter( 'image_editor_output_format', '__return_empty_array' );
+	}
+
+	/**
+	 * Tear down the class.
+	 */
+	public function tear_down() {
+		remove_filter( 'image_editor_output_format', '__return_empty_array' );
+		parent::tear_down();
 	}
 
 	/**
diff --git a/tests/phpunit/tests/image/intermediateSize.php b/tests/phpunit/tests/image/intermediateSize.php
index 830359427a..deb72c11e0 100644
--- a/tests/phpunit/tests/image/intermediateSize.php
+++ b/tests/phpunit/tests/image/intermediateSize.php
@@ -5,6 +5,15 @@
  * @group upload
  */
 class Tests_Image_Intermediate_Size extends WP_UnitTestCase {
+	/**
+	 * Set up the test fixture.
+	 */
+	public function set_up() {
+		add_filter( 'image_editor_output_format', '__return_empty_array' );
+
+		parent::set_up();
+	}
+
 	public function tear_down() {
 		$this->remove_added_uploads();
 
@@ -12,6 +21,9 @@ class Tests_Image_Intermediate_Size extends WP_UnitTestCase {
 		remove_image_size( 'false-height' );
 		remove_image_size( 'false-width' );
 		remove_image_size( 'off-by-one' );
+
+		remove_filter( 'image_editor_output_format', '__return_empty_array' );
+
 		parent::tear_down();
 	}
 
diff --git a/tests/phpunit/tests/image/resize.php b/tests/phpunit/tests/image/resize.php
index 5b302ce295..8c448c842c 100644
--- a/tests/phpunit/tests/image/resize.php
+++ b/tests/phpunit/tests/image/resize.php
@@ -14,6 +14,15 @@ abstract class WP_Tests_Image_Resize_UnitTestCase extends WP_Image_UnitTestCase
 		parent::set_up();
 
 		add_filter( 'wp_image_editors', array( $this, 'wp_image_editors' ) );
+		add_filter( 'image_editor_output_format', '__return_empty_array' );
+	}
+
+	/**
+	 * Tear down the class.
+	 */
+	public function tear_down() {
+		remove_filter( 'image_editor_output_format', '__return_empty_array' );
+		parent::tear_down();
 	}
 
 	public function wp_image_editors() {
diff --git a/tests/phpunit/tests/media.php b/tests/phpunit/tests/media.php
index ba4bedf51e..1388e6c210 100644
--- a/tests/phpunit/tests/media.php
+++ b/tests/phpunit/tests/media.php
@@ -33,7 +33,8 @@ CAP;
 		self::$_sizes                          = wp_get_additional_image_sizes();
 		$GLOBALS['_wp_additional_image_sizes'] = array();
 
-		$filename       = DIR_TESTDATA . '/images/' . self::$large_filename;
+		$filename = DIR_TESTDATA . '/images/' . self::$large_filename;
+		add_filter( 'image_editor_output_format', '__return_empty_array' );
 		self::$large_id = $factory->attachment->create_upload_object( $filename );
 
 		$post_statuses = array( 'publish', 'future', 'draft', 'auto-draft', 'trash' );
@@ -68,6 +69,7 @@ CAP;
 
 	public static function wpTearDownAfterClass() {
 		$GLOBALS['_wp_additional_image_sizes'] = self::$_sizes;
+		remove_filter( 'image_editor_output_format', '__return_empty_array' );
 	}
 
 	public static function tear_down_after_class() {
@@ -3617,6 +3619,59 @@ EOF;
 		// Clean up the above filter.
 		remove_filter( 'wp_omit_loading_attr_threshold', '__return_null', 100 );
 	}
+
+	/**
+	 * Test the wp_default_image_output_mapping function.
+	 *
+	 * @ticket 55443
+	 */
+	public function test_wp_default_image_output_mapping() {
+		$mapping = wp_default_image_output_mapping( array() );
+		$this->assertSame( array( 'image/jpeg' => 'image/webp' ), $mapping );
+	}
+
+	/**
+	 * Test that wp_default_image_output_mapping doesn't overwrite existing mappings.
+	 *
+	 * @ticket 55443
+	 */
+	public function test_wp_default_image_output_mapping_existing() {
+		$mapping = array( 'mime/png' => 'mime/webp' );
+		$mapping = wp_default_image_output_mapping( $mapping );
+		$this->assertSame(
+			array(
+				'mime/png'   => 'mime/webp',
+				'image/jpeg' => 'image/webp',
+			),
+			$mapping
+		);
+	}
+
+	/**
+	 * Test that the image editor default output for JPEGs is WebP.
+	 *
+	 * @ticket 55443
+	 */
+	public function test_wp_image_editor_default_output_maps_to_webp() {
+		remove_filter( 'image_editor_output_format', '__return_empty_array' );
+
+		$editor = wp_get_image_editor( DIR_TESTDATA . '/images/canola.jpg' );
+		$this->assertNotWPError( $editor );
+
+		$resized = $editor->resize( 100, 100, false );
+		$this->assertNotWPError( $resized );
+
+		$saved = $editor->save();
+		$this->assertNotWPError( $saved );
+
+		if ( $editor->supports_mime_type( 'image/webp' ) ) {
+			$this->assertSame( 'image/webp', $saved['mime-type'] );
+			$this->assertSame( 'canola-100x75-jpg.webp', $saved['file'] );
+		} else {
+			$this->assertSame( 'image/jpeg', $saved['mime-type'] );
+			$this->assertSame( 'canola-100x75.jpg', $saved['file'] );
+		}
+	}
 }
 
 /**
diff --git a/tests/phpunit/tests/post/attachments.php b/tests/phpunit/tests/post/attachments.php
index 2922c185d2..1bbc0c6f79 100644
--- a/tests/phpunit/tests/post/attachments.php
+++ b/tests/phpunit/tests/post/attachments.php
@@ -6,10 +6,19 @@
  * @group upload
  */
 class Tests_Post_Attachments extends WP_UnitTestCase {
+	/**
+	 * Set up the test fixture.
+	 */
+	public function set_up() {
+		add_filter( 'image_editor_output_format', '__return_empty_array' );
+
+		parent::set_up();
+	}
 
 	public function tear_down() {
 		// Remove all uploads.
 		$this->remove_added_uploads();
+		remove_filter( 'image_editor_output_format', '__return_empty_array' );
 		parent::tear_down();
 	}
 
diff --git a/tests/phpunit/tests/rest-api/rest-attachments-controller.php b/tests/phpunit/tests/rest-api/rest-attachments-controller.php
index 106906ee2b..2c97f81c05 100644
--- a/tests/phpunit/tests/rest-api/rest-attachments-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-attachments-controller.php
@@ -93,6 +93,7 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 
 		add_filter( 'rest_pre_dispatch', array( $this, 'wpSetUpBeforeRequest' ), 10, 3 );
 		add_filter( 'posts_clauses', array( $this, 'save_posts_clauses' ), 10, 2 );
+		add_filter( 'image_editor_output_format', '__return_empty_array' );
 	}
 
 	public function wpSetUpBeforeRequest( $result ) {
@@ -121,6 +122,8 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 			WP_Image_Editor_Mock::$size_return = null;
 		}
 
+		remove_filter( 'image_editor_output_format', '__return_empty_array' );
+
 		parent::tear_down();
 	}
 
