diff --git a/wp-admin/includes/class-wp-site-health.php b/wp-admin/includes/class-wp-site-health.php
index 9d3a455f23..c2f10fa72d 100644
--- a/wp-admin/includes/class-wp-site-health.php
+++ b/wp-admin/includes/class-wp-site-health.php
@@ -1502,6 +1502,8 @@ class WP_Site_Health {
 		// always rely on the latest results.
 		wp_update_https_detection_errors();
 
+		$default_update_url = wp_get_default_update_https_url();
+
 		$result = array(
 			'label'       => __( 'Your website is using an active HTTPS connection' ),
 			'status'      => 'good',
@@ -1514,9 +1516,8 @@ class WP_Site_Health {
 				__( 'An HTTPS connection is a more secure way of browsing the web. Many services now have HTTPS as a requirement. HTTPS allows you to take advantage of new features that can increase site speed, improve search rankings, and gain the trust of your visitors by helping to protect their online privacy.' )
 			),
 			'actions'     => sprintf(
-				'<p><a href="%s" target="_blank" rel="noopener">%s <span class="screen-reader-text">%s</span><span aria-hidden="true" class="dashicons dashicons-external"></span></a></p>',
-				/* translators: Documentation explaining HTTPS and why it should be used. */
-				esc_url( __( 'https://wordpress.org/support/article/why-should-i-use-https/' ) ),
+				'<p><a href="%s" target="_blank" rel="noopener">%s<span class="screen-reader-text"> %s</span><span aria-hidden="true" class="dashicons dashicons-external"></span></a></p>',
+				esc_url( $default_update_url ),
 				__( 'Learn more about why you should use HTTPS' ),
 				/* translators: Accessibility text. */
 				__( '(opens in a new tab)' )
@@ -1580,16 +1581,54 @@ class WP_Site_Health {
 					__( 'HTTPS is already supported for your website.' )
 				);
 
-				$result['actions'] = sprintf(
-					'<p><a href="%s">%s</a></p>',
-					esc_url( admin_url( 'options-general.php' ) ),
-					__( 'Update your site addresses' )
-				);
+				if ( defined( 'WP_HOME' ) || defined( 'WP_SITEURL' ) ) {
+					$result['description'] .= sprintf(
+						'<p>%s</p>',
+						sprintf(
+							/* translators: 1: wp-config.php, 2: WP_HOME, 3: WP_SITEURL */
+							__( 'However, your WordPress Address is currently controlled by a PHP constant and therefore cannot be updated. You need to edit your %1$s and remove or update the definitions of %2$s and %3$s.' ),
+							'<code>wp-config.php</code>',
+							'<code>WP_HOME</code>',
+							'<code>WP_SITEURL</code>'
+						)
+					);
+				} elseif ( current_user_can( 'update_https' ) ) {
+					$default_direct_update_url = add_query_arg( 'action', 'update_https', wp_nonce_url( admin_url( 'site-health.php' ), 'wp_update_https' ) );
+					$direct_update_url         = wp_get_direct_update_https_url();
+
+					if ( ! empty( $direct_update_url ) ) {
+						$result['actions'] = sprintf(
+							'<p class="button-container"><a class="button button-primary" href="%1$s" target="_blank" rel="noopener">%2$s<span class="screen-reader-text"> %3$s</span><span aria-hidden="true" class="dashicons dashicons-external"></span></a></p>',
+							esc_url( $direct_update_url ),
+							__( 'Update your site to use HTTPS' ),
+							/* translators: Accessibility text. */
+							__( '(opens in a new tab)' )
+						);
+					} else {
+						$result['actions'] = sprintf(
+							'<p class="button-container"><a class="button button-primary" href="%1$s">%2$s</a></p>',
+							esc_url( $default_direct_update_url ),
+							__( 'Update your site to use HTTPS' )
+						);
+					}
+				}
 			} else {
-				$result['description'] .= sprintf(
-					'<p>%s</p>',
-					__( 'Talk to your web host about supporting HTTPS for your website.' )
-				);
+				// If host-specific "Update HTTPS" URL is provided, include a link.
+				$update_url = wp_get_update_https_url();
+				if ( $update_url !== $default_update_url ) {
+					$result['description'] .= sprintf(
+						'<p><a href="%s" target="_blank" rel="noopener">%s<span class="screen-reader-text"> %s</span><span aria-hidden="true" class="dashicons dashicons-external"></span></a></p>',
+						esc_url( $update_url ),
+						__( 'Talk to your web host about supporting HTTPS for your website.' ),
+						/* translators: Accessibility text. */
+						__( '(opens in a new tab)' )
+					);
+				} else {
+					$result['description'] .= sprintf(
+						'<p>%s</p>',
+						__( 'Talk to your web host about supporting HTTPS for your website.' )
+					);
+				}
 			}
 		} elseif ( ! wp_is_https_supported() ) {
 			// If the website is using HTTPS, but HTTPS is actually not supported, inform the user about the potential
diff --git a/wp-admin/site-health.php b/wp-admin/site-health.php
index b7cc728ef6..be81b957b3 100644
--- a/wp-admin/site-health.php
+++ b/wp-admin/site-health.php
@@ -14,6 +14,8 @@ if ( isset( $_GET['tab'] ) && 'debug' === $_GET['tab'] ) {
 /** WordPress Administration Bootstrap */
 require_once __DIR__ . '/admin.php';
 
+wp_reset_vars( array( 'action' ) );
+
 $title = __( 'Site Health Status' );
 
 if ( ! current_user_can( 'view_site_health_checks' ) ) {
@@ -27,6 +29,23 @@ if ( ! class_exists( 'WP_Site_Health' ) ) {
 	require_once ABSPATH . 'wp-admin/includes/class-wp-site-health.php';
 }
 
+if ( 'update_https' === $action ) {
+	check_admin_referer( 'wp_update_https' );
+
+	if ( ! current_user_can( 'update_https' ) ) {
+		wp_die( __( 'Sorry, you are not allowed to update this site to HTTPS.' ), 403 );
+	}
+
+	if ( ! wp_is_https_supported() ) {
+		wp_die( __( 'It looks like HTTPS is not supported for your website at this point.' ) );
+	}
+
+	$result = wp_update_urls_to_https();
+
+	wp_redirect( add_query_arg( 'https_updated', (int) $result, wp_get_referer() ) );
+	exit;
+}
+
 $health_check_site_status = WP_Site_Health::get_instance();
 
 // Start by checking if this is a special request checking for the existence of certain filters.
@@ -41,6 +60,20 @@ require_once ABSPATH . 'wp-admin/admin-header.php';
 		</h1>
 	</div>
 
+	<?php
+	if ( isset( $_GET['https_updated'] ) ) {
+		if ( $_GET['https_updated'] ) {
+			?>
+			<div id="message" class="notice notice-success is-dismissible"><p><?php _e( 'Site URLs switched to HTTPS.' ); ?></p></div>
+			<?php
+		} else {
+			?>
+			<div id="message" class="notice notice-error is-dismissible"><p><?php _e( 'Site URLs could not be switched to HTTPS.' ); ?></p></div>
+			<?php
+		}
+	}
+	?>
+
 	<div class="health-check-title-section site-health-progress-wrapper loading hide-if-no-js">
 		<div class="site-health-progress">
 			<svg role="img" aria-hidden="true" focusable="false" width="100%" height="100%" viewBox="0 0 200 200" version="1.1" xmlns="http://www.w3.org/2000/svg">
diff --git a/wp-includes/capabilities.php b/wp-includes/capabilities.php
index ac976ff15c..9aecc3b06a 100644
--- a/wp-includes/capabilities.php
+++ b/wp-includes/capabilities.php
@@ -593,6 +593,14 @@ function map_meta_cap( $cap, $user_id, ...$args ) {
 				$caps[] = 'update_core';
 			}
 			break;
+		case 'update_https':
+			if ( is_multisite() && ! is_super_admin( $user_id ) ) {
+				$caps[] = 'do_not_allow';
+			} else {
+				$caps[] = 'manage_options';
+				$caps[] = 'update_core';
+			}
+			break;
 		case 'export_others_personal_data':
 		case 'erase_others_personal_data':
 		case 'manage_privacy_options':
diff --git a/wp-includes/default-filters.php b/wp-includes/default-filters.php
index 5efa182c2b..e8e0a84d45 100644
--- a/wp-includes/default-filters.php
+++ b/wp-includes/default-filters.php
@@ -176,6 +176,7 @@ add_filter( 'the_content', 'wpautop' );
 add_filter( 'the_content', 'shortcode_unautop' );
 add_filter( 'the_content', 'prepend_attachment' );
 add_filter( 'the_content', 'wp_filter_content_tags' );
+add_filter( 'the_content', 'wp_replace_insecure_home_url' );
 
 add_filter( 'the_excerpt', 'wptexturize' );
 add_filter( 'the_excerpt', 'convert_smilies' );
@@ -183,6 +184,7 @@ add_filter( 'the_excerpt', 'convert_chars' );
 add_filter( 'the_excerpt', 'wpautop' );
 add_filter( 'the_excerpt', 'shortcode_unautop' );
 add_filter( 'the_excerpt', 'wp_filter_content_tags' );
+add_filter( 'the_excerpt', 'wp_replace_insecure_home_url' );
 add_filter( 'get_the_excerpt', 'wp_trim_excerpt', 10, 2 );
 
 add_filter( 'the_post_thumbnail_caption', 'wptexturize' );
@@ -209,8 +211,11 @@ add_filter( 'widget_text_content', 'convert_smilies', 20 );
 add_filter( 'widget_text_content', 'wpautop' );
 add_filter( 'widget_text_content', 'shortcode_unautop' );
 add_filter( 'widget_text_content', 'wp_filter_content_tags' );
+add_filter( 'widget_text_content', 'wp_replace_insecure_home_url' );
 add_filter( 'widget_text_content', 'do_shortcode', 11 ); // Runs after wpautop(); note that $post global will be null when shortcodes run.
 
+add_filter( 'wp_get_custom_css', 'wp_replace_insecure_home_url' );
+
 // RSS filters.
 add_filter( 'the_title_rss', 'strip_tags' );
 add_filter( 'the_title_rss', 'ent2ncr', 8 );
@@ -347,6 +352,9 @@ add_action( 'init', 'wp_schedule_https_detection' );
 add_action( 'wp_https_detection', 'wp_update_https_detection_errors' );
 add_filter( 'cron_request', 'wp_cron_conditionally_prevent_sslverify', 9999 );
 
+// HTTPS migration.
+add_action( 'update_option_home', 'wp_update_https_migration_required', 10, 2 );
+
 // 2 Actions 2 Furious.
 add_action( 'do_feed_rdf', 'do_feed_rdf', 10, 0 );
 add_action( 'do_feed_rss', 'do_feed_rss', 10, 0 );
diff --git a/wp-includes/functions.php b/wp-includes/functions.php
index 8a5826d865..75a2463b0d 100644
--- a/wp-includes/functions.php
+++ b/wp-includes/functions.php
@@ -7580,6 +7580,91 @@ function wp_direct_php_update_button() {
 	echo '</p>';
 }
 
+/**
+ * Gets the URL to learn more about updating the site to use HTTPS.
+ *
+ * This URL can be overridden by specifying an environment variable `WP_UPDATE_HTTPS_URL` or by using the
+ * {@see 'wp_update_https_url'} filter. Providing an empty string is not allowed and will result in the
+ * default URL being used. Furthermore the page the URL links to should preferably be localized in the
+ * site language.
+ *
+ * @since 5.7.0
+ *
+ * @return string URL to learn more about updating to HTTPS.
+ */
+function wp_get_update_https_url() {
+	$default_url = wp_get_default_update_https_url();
+
+	$update_url = $default_url;
+	if ( false !== getenv( 'WP_UPDATE_HTTPS_URL' ) ) {
+		$update_url = getenv( 'WP_UPDATE_HTTPS_URL' );
+	}
+
+	/**
+	 * Filters the URL to learn more about updating the HTTPS version the site is running on.
+	 *
+	 * Providing an empty string is not allowed and will result in the default URL being used. Furthermore
+	 * the page the URL links to should preferably be localized in the site language.
+	 *
+	 * @since 5.7.0
+	 *
+	 * @param string $update_url URL to learn more about updating HTTPS.
+	 */
+	$update_url = apply_filters( 'wp_update_https_url', $update_url );
+	if ( empty( $update_url ) ) {
+		$update_url = $default_url;
+	}
+
+	return $update_url;
+}
+
+/**
+ * Gets the default URL to learn more about updating the site to use HTTPS.
+ *
+ * Do not use this function to retrieve this URL. Instead, use {@see wp_get_update_https_url()} when relying on the URL.
+ * This function does not allow modifying the returned URL, and is only used to compare the actually used URL with the
+ * default one.
+ *
+ * @since 5.7.0
+ * @access private
+ *
+ * @return string Default URL to learn more about updating to HTTPS.
+ */
+function wp_get_default_update_https_url() {
+	/* translators: Documentation explaining HTTPS and why it should be used. */
+	return __( 'https://wordpress.org/support/article/why-should-i-use-https/' );
+}
+
+/**
+ * Gets the URL for directly updating the site to use HTTPS.
+ *
+ * A URL will only be returned if the `WP_DIRECT_UPDATE_HTTPS_URL` environment variable is specified or
+ * by using the {@see 'wp_direct_update_https_url'} filter. This allows hosts to send users directly to
+ * the page where they can update their site to use HTTPS.
+ *
+ * @since 5.7.0
+ *
+ * @return string URL for directly updating to HTTPS or empty string.
+ */
+function wp_get_direct_update_https_url() {
+	$direct_update_url = '';
+
+	if ( false !== getenv( 'WP_DIRECT_UPDATE_HTTPS_URL' ) ) {
+		$direct_update_url = getenv( 'WP_DIRECT_UPDATE_HTTPS_URL' );
+	}
+
+	/**
+	 * Filters the URL for directly updating the PHP version the site is running on from the host.
+	 *
+	 * @since 5.7.0
+	 *
+	 * @param string $direct_update_url URL for directly updating PHP.
+	 */
+	$direct_update_url = apply_filters( 'wp_direct_update_https_url', $direct_update_url );
+
+	return $direct_update_url;
+}
+
 /**
  * Get the size of a directory.
  *
diff --git a/wp-includes/https-migration.php b/wp-includes/https-migration.php
new file mode 100644
index 0000000000..b8b80d63f0
--- /dev/null
+++ b/wp-includes/https-migration.php
@@ -0,0 +1,140 @@
+<?php
+/**
+ * HTTPS migration functions.
+ *
+ * @package WordPress
+ * @since 5.7.0
+ */
+
+/**
+ * Checks whether WordPress should replace old HTTP URLs to the site with their HTTPS counterpart.
+ *
+ * If a WordPress site had its URL changed from HTTP to HTTPS, by default this will return `true`, causing WordPress to
+ * add frontend filters to replace insecure site URLs that may be present in older database content. The
+ * {@see 'wp_should_replace_insecure_home_url'} filter can be used to modify that behavior.
+ *
+ * @since 5.7.0
+ *
+ * @return bool True if insecure URLs should replaced, false otherwise.
+ */
+function wp_should_replace_insecure_home_url() {
+	$should_replace_insecure_home_url = wp_is_using_https()
+		&& get_option( 'https_migration_required' )
+		// For automatic replacement, both 'home' and 'siteurl' need to not only use HTTPS, they also need to be using
+		// the same domain.
+		&& wp_parse_url( home_url(), PHP_URL_HOST ) === wp_parse_url( site_url(), PHP_URL_HOST );
+
+	/**
+	 * Filters whether WordPress should replace old HTTP URLs to the site with their HTTPS counterpart.
+	 *
+	 * If a WordPress site had its URL changed from HTTP to HTTPS, by default this will return `true`. This filter can
+	 * be used to disable that behavior, e.g. after having replaced URLs manually in the database.
+	 *
+	 * @since 5.7.0
+	 *
+	 * @param bool $should_replace_insecure_home_url Whether insecure HTTP URLs to the site should be replaced.
+	 */
+	return apply_filters( 'wp_should_replace_insecure_home_url', $should_replace_insecure_home_url );
+}
+
+/**
+ * Replaces insecure HTTP URLs to the site in the given content, if configured to do so.
+ *
+ * This function replaces all occurrences of the HTTP version of the site's URL with its HTTPS counterpart, if
+ * determined via {@see wp_should_replace_insecure_home_url()}.
+ *
+ * @since 5.7.0
+ *
+ * @param string $content Content to replace URLs in.
+ * @return string Filtered content.
+ */
+function wp_replace_insecure_home_url( $content ) {
+	if ( ! wp_should_replace_insecure_home_url() ) {
+		return $content;
+	}
+
+	$https_url = home_url( '', 'https' );
+	$http_url  = str_replace( 'https://', 'http://', $https_url );
+
+	// Also replace potentially escaped URL.
+	$escaped_https_url = str_replace( '/', '\/', $https_url );
+	$escaped_http_url  = str_replace( '/', '\/', $http_url );
+
+	return str_replace(
+		array(
+			$http_url,
+			$escaped_http_url,
+		),
+		array(
+			$https_url,
+			$escaped_https_url,
+		),
+		$content
+	);
+}
+
+/**
+ * Update the 'home' and 'siteurl' option to use the HTTPS variant of their URL.
+ *
+ * If this update does not result in WordPress recognizing that the site is now using HTTPS (e.g. due to constants
+ * overriding the URLs used), the changes will be reverted. In such a case the function will return false.
+ *
+ * @since 5.7.0
+ *
+ * @return bool True on success, false on failure.
+ */
+function wp_update_urls_to_https() {
+	// Get current URL options.
+	$orig_home    = get_option( 'home' );
+	$orig_siteurl = get_option( 'siteurl' );
+
+	// Get current URL options, replacing HTTP with HTTPS.
+	$home    = str_replace( 'http://', 'https://', $orig_home );
+	$siteurl = str_replace( 'http://', 'https://', $orig_siteurl );
+
+	// Update the options.
+	update_option( 'home', $home );
+	update_option( 'siteurl', $siteurl );
+
+	if ( ! wp_is_using_https() ) {
+		// If this did not result in the site recognizing HTTPS as being used,
+		// revert the change and return false.
+		update_option( 'home', $orig_home );
+		update_option( 'siteurl', $orig_siteurl );
+		return false;
+	}
+
+	// Otherwise the URLs were successfully changed to use HTTPS.
+	return true;
+}
+
+/**
+ * Updates the 'https_migration_required' option if needed when the given URL has been updated from HTTP to HTTPS.
+ *
+ * If this is a fresh site, a migration will not be required, so the option will be set as `false`.
+ *
+ * This is hooked into the {@see 'update_option_home'} action.
+ *
+ * @since 5.7.0
+ * @access private
+ *
+ * @param mixed $old_url Previous value of the URL option.
+ * @param mixed $new_url New value of the URL option.
+ */
+function wp_update_https_migration_required( $old_url, $new_url ) {
+	// Do nothing if WordPress is being installed.
+	if ( wp_installing() ) {
+		return;
+	}
+
+	// Delete/reset the option if the new URL is not the HTTPS version of the old URL.
+	if ( untrailingslashit( (string) $old_url ) !== str_replace( 'https://', 'http://', untrailingslashit( (string) $new_url ) ) ) {
+		delete_option( 'https_migration_required' );
+		return;
+	}
+
+	// If this is a fresh site, there is no content to migrate, so do not require migration.
+	$https_migration_required = get_option( 'fresh_site' ) ? false : true;
+
+	update_option( 'https_migration_required', $https_migration_required );
+}
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 88b56f0942..8361775ad3 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.7-alpha-50130';
+$wp_version = '5.7-alpha-50131';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.
diff --git a/wp-settings.php b/wp-settings.php
index c5c3a56ee9..7b85597be6 100644
--- a/wp-settings.php
+++ b/wp-settings.php
@@ -172,6 +172,7 @@ require ABSPATH . WPINC . '/theme.php';
 require ABSPATH . WPINC . '/class-wp-theme.php';
 require ABSPATH . WPINC . '/template.php';
 require ABSPATH . WPINC . '/https-detection.php';
+require ABSPATH . WPINC . '/https-migration.php';
 require ABSPATH . WPINC . '/class-wp-user-request.php';
 require ABSPATH . WPINC . '/user.php';
 require ABSPATH . WPINC . '/class-wp-user-query.php';