diff --git a/src/wp-includes/html-api/class-wp-html-processor.php b/src/wp-includes/html-api/class-wp-html-processor.php
index 4dd7d0e492d9e..f652900e2455d 100644
--- a/src/wp-includes/html-api/class-wp-html-processor.php
+++ b/src/wp-includes/html-api/class-wp-html-processor.php
@@ -417,6 +417,84 @@ public function next_tag( $query = null ) {
 		return false;
 	}
 
+	/**
+	 * Returns the raw HTMl content inside a matched tag.
+	 *
+	 * @since 6.4.0
+	 *
+	 * @throws Exception When unable to allocate a bookmark for internal tracking of the open tag.
+	 *
+	 * @return string|null The inner HTML if available, else NULL.
+	 */
+	public function get_inner_markup() {
+		if ( null === $this->get_tag() ) {
+			return null;
+		}
+
+		$start = $this->current_token;
+		parent::set_bookmark( 'start' );
+		// @TODO: add after-pop hook to turn this into a constant boolean check.
+		do {
+			$found_tag = $this->step();
+		} while ( $found_tag && $this->state->stack_of_open_elements->contains_node( $start ) );
+
+		/*
+		 * If there's no tag to bookmark then it means the opened tag has no closing
+		 * and the rest of the document is contained within the inner HTML.
+		 */
+		if ( ! $found_tag ) {
+			$inner_html = $this->substr_bookmark( 'after', 'start' );
+			parent::release_bookmark( 'start' );
+		} else {
+			parent::set_bookmark( 'end' );
+			$inner_html = $this->substr_bookmarks( 'after', 'start', 'before', 'end' );
+			parent::release_bookmark( 'start' );
+			parent::release_bookmark( 'end' );
+		}
+
+		return $inner_html;
+	}
+
+	/**
+	 * Returns the raw HTMl content inside a matched tag.
+	 *
+	 * @since 6.4.0
+	 *
+	 * @throws Exception When unable to allocate a bookmark for internal tracking of the open tag.
+	 *
+	 * @return string|null The inner HTML if available, else NULL.
+	 */
+	public function get_outer_markup() {
+		if ( null === $this->get_tag() ) {
+			return null;
+		}
+
+		$start = $this->current_token;
+		parent::set_bookmark( 'start' );
+		// @TODO: add after-pop hook to turn this into a constant boolean check.
+		do {
+			$found_tag = $this->step();
+		} while ( $found_tag && $this->state->stack_of_open_elements->contains_node( $start ) );
+
+		/*
+		 * If there's no tag to bookmark then it means the opened tag has no closing
+		 * and the rest of the document is contained within the inner HTML.
+		 */
+		if ( ! $found_tag ) {
+			$inner_html = $this->substr_bookmark( 'before', 'start' );
+		} else {
+			parent::set_bookmark( 'end' );
+			$did_close    = $this->get_tag() === $start->node_name && $this->is_tag_closer();
+			$end_position = $did_close ? 'after' : 'before';
+			$inner_html   = $this->substr_bookmarks( 'before', 'start', $end_position, 'end' );
+		}
+
+		parent::release_bookmark( 'start' );
+		parent::release_bookmark( 'end' );
+
+		return $inner_html;
+	}
+
 	/**
 	 * Steps through the HTML document and stop at the next tag, if any.
 	 *
@@ -437,12 +515,9 @@ public function step( $node_to_process = self::PROCESS_NEXT_NODE ) {
 				$this->state->stack_of_open_elements->pop();
 			}
 
-			parent::next_tag( self::VISIT_EVERYTHING );
-		}
-
-		// Finish stepping when there are no more tokens in the document.
-		if ( null === $this->get_tag() ) {
-			return false;
+			if ( ! parent::next_tag( self::VISIT_EVERYTHING ) ) {
+				return false;
+			}
 		}
 
 		$this->current_token = new WP_HTML_Token(
@@ -722,6 +797,42 @@ private function bookmark_tag() {
 		return "{$this->bookmark_counter}";
 	}
 
+	/**
+	 * Returns a substring of the input HTML document from a bookmark until the end.
+	 *
+	 * @since 6.4.0
+	 *
+	 * @param string $start_position "before" to clip before bookmark, "after" to clip after.
+	 * @param string $start          Bookmark name at which to start clipping.
+	 * @return string Clipped substring of input HTMl document.
+	 */
+	private function substr_bookmark( $start_position, $start ) {
+		$start_bookmark = $this->bookmarks[ $start ];
+		$start_offset   = 'before' === $start_position ? $start_bookmark->start : $start_bookmark->end + 1;
+
+		return substr( $this->html, $start_offset );
+	}
+
+	/**
+	 * Returns a substring of the input HTML document delimited by bookmarks.
+	 *
+	 * @since 6.4.0
+	 *
+	 * @param string $start_position "before" to clip before bookmark, "after" to clip after.
+	 * @param string $start          Bookmark name at which to start clipping.
+	 * @param string $end_position   "before" to clip before bookmark, "after" to clip after.
+	 * @param string $end            Bookmark name at which to end clipping.
+	 * @return string Clipped substring of input HTMl document.
+	 */
+	private function substr_bookmarks( $start_position, $start, $end_position, $end ) {
+		$start_bookmark = $this->bookmarks[ $start ];
+		$end_bookmark   = $this->bookmarks[ $end ];
+		$start_offset   = 'before' === $start_position ? $start_bookmark->start : $start_bookmark->end + 1;
+		$end_offset     = 'before' === $end_position ? $end_bookmark->start : $end_bookmark->end + 1;
+
+		return substr( $this->html, $start_offset, $end_offset - $start_offset );
+	}
+
 	/*
 	 * HTML semantic overrides for Tag Processor
 	 */
diff --git a/tests/phpunit/tests/html-api/wpHtmlProcessorGetInnerMarkup.php b/tests/phpunit/tests/html-api/wpHtmlProcessorGetInnerMarkup.php
new file mode 100644
index 0000000000000..d16aac6f9cc91
--- /dev/null
+++ b/tests/phpunit/tests/html-api/wpHtmlProcessorGetInnerMarkup.php
@@ -0,0 +1,93 @@
+<?php
+/**
+ * Unit tests covering WP_HTML_Processor::get_inner_markup()
+ *
+ * @package WordPress
+ * @subpackage HTML-API
+ *
+ * @since 6.4.0
+ *
+ * @group html-api
+ *
+ * @coversDefaultClass WP_HTML_Processor
+ */
+class Tests_HtmlApi_WpHtmlProcessorGetInnerMarkup extends WP_UnitTestCase {
+	/**
+	 * @ticket {TICKET_NUMBER}
+	 *
+	 * @covers WP_HTML_Processor::get_inner_markup
+	 *
+	 * @since 6.4.0
+	 */
+	public function test_returns_null_when_not_on_a_matching_tag() {
+		$p = WP_HTML_Processor::createFragment( '<p><div><span></span></div>' );
+
+		$this->assertNull( $p->get_inner_markup() );
+
+		$this->assertFalse( $p->next_tag( 'BUTTON' ), "Should not have found a BUTTON tag but stopped at {$p->get_tag()}." );
+		$this->assertNull( $p->get_inner_markup() );
+	}
+
+	/**
+	 * @ticket {TICKET_NUMBER}
+	 *
+	 * @covers WP_HTML_Processor::get_inner_markup
+	 *
+	 * @dataProvider data_html_with_inner_markup
+	 *
+	 * @since 6.4.0
+	 *
+	 * @param string $html_with_target_node HTML containing a node with the `target` attribute set.
+	 * @param string $expected_inner_markup Inner markup of target node.
+	 */
+	public function test_returns_appropriate_inner_markup( $html_with_target_node, $expected_inner_markup ) {
+		$p = WP_HTML_Processor::createFragment( $html_with_target_node );
+
+		while ( $p->next_tag() && null === $p->get_attribute( 'target' ) ) {
+			continue;
+		}
+
+		$this->assertSame( $expected_inner_markup, $p->get_inner_markup(), 'Failed to return appropriate inner markup.' );
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array[]
+	 */
+	public function data_html_with_inner_markup() {
+		$data = array(
+			'Empty elements'               => array( '<div target></div>', '' ),
+			'Element containing only text' => array( '<div target>inside</div>', 'inside' ),
+			'Element with nested tags'     => array( '<div target>inside <span>the</span> div</div>', 'inside <span>the</span> div' ),
+			'Unclosed element'             => array( '<div target>This is <em>all</em> inside the DIV', 'This is <em>all</em> inside the DIV' ),
+			'Partially-closed element'     => array( '<div target>This is <em>all</em> inside the DIV</div', 'This is <em>all</em> inside the DIV</div' ),
+			'Implicitly-closed element'    => array( '<div><p target>Inside the P</div>Outside the P</p>', 'Inside the P' ),
+		);
+
+		$inner_html = <<<HTML
+			<p>This is inside the <strong>Match</strong></p>
+			<p><img></p>
+			<div>
+				<figure>
+					<img>
+					<figcaption>Look at the <strike>picture</strike> photograph.</figcaption>
+				</figure>
+			</div>
+HTML;
+
+		$html = <<<HTML
+			<div>
+					<p>This is not in the match.
+					<p>This is another paragraph not <a href="#">in</a> the match.
+				</div>
+				<div target>{$inner_html}</div>
+				<div>
+					<p>This is also note in the match.</p>
+				</div>
+HTML;
+		$data['Complicated inner nesting'] = array( $html, $inner_html );
+
+		return $data;
+	}
+}
diff --git a/tests/phpunit/tests/html-api/wpHtmlProcessorGetOuterMarkup.php b/tests/phpunit/tests/html-api/wpHtmlProcessorGetOuterMarkup.php
new file mode 100644
index 0000000000000..8536cf4ea1ea7
--- /dev/null
+++ b/tests/phpunit/tests/html-api/wpHtmlProcessorGetOuterMarkup.php
@@ -0,0 +1,95 @@
+<?php
+/**
+ * Unit tests covering WP_HTML_Processor::get_outer_html()
+ *
+ * @package WordPress
+ * @subpackage HTML-API
+ *
+ * @since 6.4.0
+ *
+ * @group html-api
+ *
+ * @coversDefaultClass WP_HTML_Processor
+ */
+class Tests_HtmlApi_WpHtmlProcessorGetOuterMarkup extends WP_UnitTestCase {
+	/**
+	 * Ensures that it's not possible to get inner contents when not stopped at a tag in the HTML.
+	 *
+	 * @ticket {TICKET_NUMBER}
+	 *
+	 * @covers WP_HTML_Processor::get_outer_markup
+	 *
+	 * @since 6.4.0
+	 */
+	public function test_returns_null_when_not_on_a_matching_tag() {
+		$p = WP_HTML_Processor::createFragment( '<p><div><span></span></div>' );
+
+		$this->assertNull( $p->get_outer_markup() );
+
+		$this->assertFalse( $p->next_tag( 'BUTTON' ), "Should not have found a BUTTON tag but stopped at {$p->get_tag()}." );
+		$this->assertNull( $p->get_outer_markup() );
+	}
+
+	/**
+	 * @ticket {TICKET_NUMBER}
+	 *
+	 * @covers WP_HTML_Processor::get_outer_markup
+	 *
+	 * @dataProvider data_html_with_outer_markup
+	 *
+	 * @since 6.4.0
+	 *
+	 * @param string $html_with_target_node HTML containing a node with the `target` attribute set.
+	 * @param string $expected_outer_markup Outer markup of target node.
+	 */
+	public function test_returns_appropriate_outer_markup( $html_with_target_node, $expected_outer_markup ) {
+		$p = WP_HTML_Processor::createFragment( $html_with_target_node );
+
+		while ( $p->next_tag() && null === $p->get_attribute( 'target' ) ) {
+			continue;
+		}
+
+		$this->assertSame( $expected_outer_markup, $p->get_outer_markup(), 'Failed to return appropriate inner markup.' );
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array[]
+	 */
+	public function data_html_with_outer_markup() {
+		$data = array(
+			'Empty elements'               => array( '<div target></div>', '<div target></div>' ),
+			'Element containing only text' => array( '<div target>inside</div>', '<div target>inside</div>' ),
+			'Element with nested tags'     => array( '<div target>inside <span>the</span> div</div>', '<div target>inside <span>the</span> div</div>' ),
+			'Unclosed element'             => array( '<div target>This is <em>all</em> inside the DIV', '<div target>This is <em>all</em> inside the DIV' ),
+			'Partially-closed element'     => array( '<div target>This is <em>all</em> inside the DIV</div', '<div target>This is <em>all</em> inside the DIV</div' ),
+			'Implicitly-closed element'    => array( '<div><p target>Inside the P</div>Outside the P</p>', '<p target>Inside the P' ),
+		);
+
+		$inner_html = <<<HTML
+			<p>This is inside the <strong>Match</strong></p>
+			<p><img></p>
+			<div>
+				<figure>
+					<img>
+					<figcaption>Look at the <strike>picture</strike> photograph.</figcaption>
+				</figure>
+			</div>
+HTML;
+
+		$html = <<<HTML
+			<div>
+				<p>This is not in the match.
+				<p>This is another paragraph not <a href="#">in</a> the match.
+			</div>
+			<div target>{$inner_html}</div>
+			<div>
+				<p>This is also note in the match.</p>
+			</div>
+HTML;
+		$data['Complicated inner nesting'] = array( $html, "<div target>{$inner_html}</div>" );
+
+		return $data;
+	}
+}