Index: wp-content/themes/twentyfifteen/author-bio.php
===================================================================
--- wp-content/themes/twentyfifteen/author-bio.php	(revision 29989)
+++ wp-content/themes/twentyfifteen/author-bio.php	(working copy)
@@ -24,7 +24,7 @@
 		?>
 	</div><!-- .author-avatar -->
 	<div class="author-description">
-		<h2 class="author-title"><?php echo get_the_author(); ?></h2>
+		<h3 class="author-title"><?php echo get_the_author(); ?></h3>
 		<p class="author-bio">
 			<?php the_author_meta( 'description' ); ?>
 			<a class="author-link" href="<?php echo esc_url( get_author_posts_url( get_the_author_meta( 'ID' ) ) ); ?>" rel="author">
Index: wp-content/themes/twentyfifteen/content-link.php
===================================================================
--- wp-content/themes/twentyfifteen/content-link.php	(revision 29989)
+++ wp-content/themes/twentyfifteen/content-link.php	(working copy)
@@ -14,7 +14,7 @@
 	<?php twentyfifteen_post_thumbnail(); ?>
 
 	<header class="entry-header">
-		<?php the_title( sprintf( '<h1 class="entry-title"><a href="%s" rel="bookmark">', esc_url( twentyfifteen_get_link_url() ) ), '</a></h1>' ); ?>
+		<?php the_title( sprintf( '<h2 class="entry-title"><a href="%s" rel="bookmark">', esc_url( twentyfifteen_get_link_url() ) ), '</a></h2>' ); ?>
 	</header>
 	<!-- .entry-header -->
 
Index: wp-content/themes/twentyfifteen/content-search.php
===================================================================
--- wp-content/themes/twentyfifteen/content-search.php	(revision 29989)
+++ wp-content/themes/twentyfifteen/content-search.php	(working copy)
@@ -14,7 +14,7 @@
 	<?php twentyfifteen_post_thumbnail(); ?>
 
 	<header class="entry-header">
-		<?php the_title( sprintf( '<h1 class="entry-title"><a href="%s" rel="bookmark">', esc_url( get_permalink() ) ), '</a></h1>' ); ?>
+		<?php the_title( sprintf( '<h2 class="entry-title"><a href="%s" rel="bookmark">', esc_url( get_permalink() ) ), '</a></h2>' ); ?>
 	</header><!-- .entry-header -->
 
 	<div class="entry-summary">
Index: wp-content/themes/twentyfifteen/content.php
===================================================================
--- wp-content/themes/twentyfifteen/content.php	(revision 29989)
+++ wp-content/themes/twentyfifteen/content.php	(working copy)
@@ -15,10 +15,10 @@
 
 	<header class="entry-header">
 		<?php
-			if ( is_single() ) :
+			if ( is_singular() ) :
 				the_title( '<h1 class="entry-title">', '</h1>' );
 			else :
-				the_title( sprintf( '<h1 class="entry-title"><a href="%s" rel="bookmark">', esc_url( get_permalink() ) ), '</a></h1>' );
+				the_title( sprintf( '<h2 class="entry-title"><a href="%s" rel="bookmark">', esc_url( get_permalink() ) ), '</a></h2>' );
 			endif;
 		?>
 	</header><!-- .entry-header -->
Index: wp-content/themes/twentyfifteen/functions.php
===================================================================
--- wp-content/themes/twentyfifteen/functions.php	(revision 29989)
+++ wp-content/themes/twentyfifteen/functions.php	(working copy)
@@ -119,8 +119,8 @@
 		'description'   => __( 'Add widgets here to appear in your sidebar.', 'twentyfifteen' ),
 		'before_widget' => '<aside id="%1$s" class="widget %2$s">',
 		'after_widget'  => '</aside>',
-		'before_title'  => '<h1 class="widget-title">',
-		'after_title'   => '</h1>',
+		'before_title'  => '<h2 class="widget-title">',
+		'after_title'   => '</h2>',
 	) );
 }
 add_action( 'widgets_init', 'twentyfifteen_widgets_init' );
Index: wp-content/themes/twentyfifteen/image.php
===================================================================
--- wp-content/themes/twentyfifteen/image.php	(revision 29989)
+++ wp-content/themes/twentyfifteen/image.php	(working copy)
@@ -22,7 +22,7 @@
 					</nav><!-- .image-navigation -->
 
 					<header class="entry-header">
-						<?php the_title( '<h1 class="entry-title">', '</h1>' ); ?>
+						<?php the_title( '<h2 class="entry-title">', '</h2>' ); ?>
 					</header><!-- .entry-header -->
 
 					<div class="entry-content">
Index: wp-content/themes/twentyfifteen/inc/template-tags.php
===================================================================
--- wp-content/themes/twentyfifteen/inc/template-tags.php	(revision 29989)
+++ wp-content/themes/twentyfifteen/inc/template-tags.php	(working copy)
@@ -34,7 +34,7 @@
 	if ( $links ) :
 	?>
 	<nav class="navigation pagination" role="navigation">
-		<h1 class="screen-reader-text"><?php esc_html_e( 'Posts navigation', 'twentyfifteen' ); ?></h1>
+		<h2 class="screen-reader-text"><?php esc_html_e( 'Posts navigation', 'twentyfifteen' ); ?></h2>
 		<div class="nav-links">
 			<?php echo $links; ?>
 		</div><!-- .nav-links -->
@@ -71,7 +71,7 @@
 
 	?>
 	<nav class="navigation post-navigation" role="navigation">
-		<h1 class="screen-reader-text"><?php esc_html_e( 'Post navigation', 'twentyfifteen' ); ?></h1>
+		<h2 class="screen-reader-text"><?php esc_html_e( 'Post navigation', 'twentyfifteen' ); ?></h2>
 		<div class="nav-links">
 			<?php
 			if ( is_attachment() ) :
@@ -98,7 +98,7 @@
 	if ( get_comment_pages_count() > 1 && get_option( 'page_comments' ) ) :
 	?>
 	<nav class="navigation comment-navigation" role="navigation">
-		<h1 class="screen-reader-text"><?php esc_html_e( 'Comment navigation', 'twentyfifteen' ); ?></h1>
+		<h2 class="screen-reader-text"><?php esc_html_e( 'Comment navigation', 'twentyfifteen' ); ?></h2>
 		<div class="nav-links">
 			<?php
 				if ( $prev_link = get_previous_comments_link( esc_html__( 'Older Comments', 'twentyfifteen' ) ) ) :