diff --git a/wp-admin/includes/admin-filters.php b/wp-admin/includes/admin-filters.php
index e80c111dde..f5f9600332 100644
--- a/wp-admin/includes/admin-filters.php
+++ b/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/wp-admin/includes/image-edit.php b/wp-admin/includes/image-edit.php
index e814fc47e7..9c71e68794 100644
--- a/wp-admin/includes/image-edit.php
+++ b/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/wp-admin/includes/media.php b/wp-admin/includes/media.php
index 51f21ddb7d..3e2093ac2b 100644
--- a/wp-admin/includes/media.php
+++ b/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/wp-includes/class-wp-image-editor.php b/wp-includes/class-wp-image-editor.php
index caa3092d36..15e4aa8d6e 100644
--- a/wp-includes/class-wp-image-editor.php
+++ b/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
+	 * @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
-	 * @param string $dest_path
-	 * @param string $extension
-	 * @return string filename
+	 * @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/wp-includes/version.php b/wp-includes/version.php
index a839b7c54b..00fe2ce1c9 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.1-alpha-54085';
+$wp_version = '6.1-alpha-54086';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.