diff --git a/src/js/media/controllers/library.js b/src/js/media/controllers/library.js
index 91bdeea656f95..db77c8dae8241 100644
--- a/src/js/media/controllers/library.js
+++ b/src/js/media/controllers/library.js
@@ -196,7 +196,7 @@ Library = wp.media.controller.State.extend(/** @lends wp.media.controller.Librar
 	isImageAttachment: function( attachment ) {
 		// If uploading, we know the filename but not the mime type.
 		if ( attachment.get('uploading') ) {
-			return /\.(jpe?g|png|gif|webp|avif|heic)$/i.test( attachment.get('filename') );
+			return /\.(jpe?g|png|gif|webp|avif|heic|heif)$/i.test( attachment.get('filename') );
 		}
 
 		return attachment.get('type') === 'image';
diff --git a/src/wp-includes/class-wp-image-editor-imagick.php b/src/wp-includes/class-wp-image-editor-imagick.php
index 81591dd981158..4370e30a3e528 100644
--- a/src/wp-includes/class-wp-image-editor-imagick.php
+++ b/src/wp-includes/class-wp-image-editor-imagick.php
@@ -271,7 +271,7 @@ protected function update_size( $width = null, $height = null ) {
 		 * If we still don't have the image size, fall back to `wp_getimagesize`. This ensures AVIF and HEIC images
 		 * are properly sized without affecting previous `getImageGeometry` behavior.
 		 */
-		if ( ( ! $width || ! $height ) && ( 'image/avif' === $this->mime_type || 'image/heic' === $this->mime_type ) ) {
+		if ( ( ! $width || ! $height ) && ( 'image/avif' === $this->mime_type || wp_is_heic_image_mime_type( $this->mime_type ) ) ) {
 			$size   = wp_getimagesize( $this->file );
 			$width  = $size[0];
 			$height = $size[1];
diff --git a/src/wp-includes/functions.php b/src/wp-includes/functions.php
index a5720fc10ad43..aea82e76c96e2 100644
--- a/src/wp-includes/functions.php
+++ b/src/wp-includes/functions.php
@@ -3101,7 +3101,13 @@ function wp_check_filetype_and_ext( $file, $filename, $mimes = null ) {
 		// Attempt to figure out what type of image it actually is.
 		$real_mime = wp_get_image_mime( $file );
 
-		if ( $real_mime && $real_mime !== $type ) {
+		$heic_images_etx = array(
+			'heif',
+			'heics',
+			'heifs',
+		);
+
+		if ( $real_mime && ( $real_mime !== $type || in_array( $ext, $heic_images_etx, true ) ) ) {
 			/**
 			 * Filters the list mapping image mime types to their respective extensions.
 			 *
@@ -3119,13 +3125,24 @@ function wp_check_filetype_and_ext( $file, $filename, $mimes = null ) {
 					'image/tiff' => 'tif',
 					'image/webp' => 'webp',
 					'image/avif' => 'avif',
+
+					/*
+					 * In theory there are/should be file extensions that correspond to the
+					 * mime types: .heif, .heics and .heifs. However it seems that HEIC images
+					 * with any of the mime types commonly have a .heic file extension.
+					 * Seems keeping the status quo here is best for compatibility.
+					 */
 					'image/heic' => 'heic',
+					'image/heif' => 'heic',
+					'image/heic-sequence' => 'heic',
+					'image/heif-sequence' => 'heic',
 				)
 			);
 
 			// Replace whatever is after the last period in the filename with the correct extension.
 			if ( ! empty( $mime_to_ext[ $real_mime ] ) ) {
 				$filename_parts = explode( '.', $filename );
+
 				array_pop( $filename_parts );
 				$filename_parts[] = $mime_to_ext[ $real_mime ];
 				$new_filename     = implode( '.', $filename_parts );
@@ -3316,9 +3333,7 @@ function wp_get_image_mime( $file ) {
 			$mime      = ( $imagetype ) ? image_type_to_mime_type( $imagetype ) : false;
 		} elseif ( function_exists( 'getimagesize' ) ) {
 			// Don't silence errors when in debug mode, unless running unit tests.
-			if ( defined( 'WP_DEBUG' ) && WP_DEBUG
-				&& ! defined( 'WP_RUN_CORE_TESTS' )
-			) {
+			if ( defined( 'WP_DEBUG' ) && WP_DEBUG && ! defined( 'WP_RUN_CORE_TESTS' ) ) {
 				// Not using wp_getimagesize() here to avoid an infinite loop.
 				$imagesize = getimagesize( $file );
 			} else {
@@ -3365,22 +3380,28 @@ function wp_get_image_mime( $file ) {
 		// Divide the header string into 4 byte groups.
 		$magic = str_split( $magic, 8 );
 
-		if (
-			isset( $magic[1] ) &&
-			isset( $magic[2] ) &&
-			'ftyp' === hex2bin( $magic[1] ) &&
-			( 'avif' === hex2bin( $magic[2] ) || 'avis' === hex2bin( $magic[2] ) )
-		) {
-			$mime = 'image/avif';
-		}
+		if ( isset( $magic[1] ) && isset( $magic[2] ) && 'ftyp' === hex2bin( $magic[1] ) ) {
+			if ( 'avif' === hex2bin( $magic[2] ) || 'avis' === hex2bin( $magic[2] ) ) {
+				$mime = 'image/avif';
+			} elseif ( 'heic' === hex2bin( $magic[2] ) ) {
+				$mime = 'image/heic';
+			} elseif ( 'heif' === hex2bin( $magic[2] ) ) {
+				$mime = 'image/heif';
+			} else {
+				/*
+				 * HEIC/HEIF images and image sequences/animations may have other strings here
+				 * like mif1, msf1, etc. For now fall back to using finfo_file() to detect these.
+				 */
+				if ( extension_loaded( 'fileinfo' ) ) {
+					$fileinfo  = finfo_open( FILEINFO_MIME_TYPE );
+					$mime_type = finfo_file( $fileinfo, $file );
+					finfo_close( $fileinfo );
 
-		if (
-			isset( $magic[1] ) &&
-			isset( $magic[2] ) &&
-			'ftyp' === hex2bin( $magic[1] ) &&
-			( 'heic' === hex2bin( $magic[2] ) || 'heif' === hex2bin( $magic[2] ) )
-		) {
-			$mime = 'image/heic';
+					if ( wp_is_heic_image_mime_type( $mime_type ) ) {
+						$mime = $mime_type;
+					}
+				}
+			}
 		}
 	} catch ( Exception $e ) {
 		$mime = false;
@@ -3423,7 +3444,13 @@ function wp_get_mime_types() {
 			'webp'                         => 'image/webp',
 			'avif'                         => 'image/avif',
 			'ico'                          => 'image/x-icon',
+
+			// TODO: Needs improvement. All images with the following mime types seem to have .heic file extension.
 			'heic'                         => 'image/heic',
+			'heif'                         => 'image/heif',
+			'heics'                        => 'image/heic-sequence',
+			'heifs'                        => 'image/heif-sequence',
+
 			// Video formats.
 			'asf|asx'                      => 'video/x-ms-asf',
 			'wmv'                          => 'video/x-ms-wmv',
@@ -3543,7 +3570,7 @@ function wp_get_ext_types() {
 	return apply_filters(
 		'ext2type',
 		array(
-			'image'       => array( 'jpg', 'jpeg', 'jpe', 'gif', 'png', 'bmp', 'tif', 'tiff', 'ico', 'heic', 'webp', 'avif' ),
+			'image'       => array( 'jpg', 'jpeg', 'jpe', 'gif', 'png', 'bmp', 'tif', 'tiff', 'ico', 'heic', 'heif', 'webp', 'avif' ),
 			'audio'       => array( 'aac', 'ac3', 'aif', 'aiff', 'flac', 'm3a', 'm4a', 'm4b', 'mka', 'mp1', 'mp2', 'mp3', 'ogg', 'oga', 'ram', 'wav', 'wma' ),
 			'video'       => array( '3g2', '3gp', '3gpp', 'asf', 'avi', 'divx', 'dv', 'flv', 'm4v', 'mkv', 'mov', 'mp4', 'mpeg', 'mpg', 'mpv', 'ogm', 'ogv', 'qt', 'rm', 'vob', 'wmv' ),
 			'document'    => array( 'doc', 'docx', 'docm', 'dotm', 'odt', 'pages', 'pdf', 'xps', 'oxps', 'rtf', 'wp', 'wpd', 'psd', 'xcf' ),
@@ -9037,3 +9064,22 @@ function wp_admin_notice( $message, $args = array() ) {
 
 	echo wp_kses_post( wp_get_admin_notice( $message, $args ) );
 }
+
+/**
+ * Checks if a mime type is for a HEIC/HEIF image.
+ *
+ * @since 6.7.0
+ *
+ * @param string $mime_type The mime type to check.
+ * @return bool Whether the mime type is for a HEIC/HEIF image.
+ */
+function wp_is_heic_image_mime_type( $mime_type ) {
+	$heic_mime_types = array(
+		'image/heic',
+		'image/heif',
+		'image/heic-sequence',
+		'image/heif-sequence',
+	);
+
+	return in_array( $mime_type, $heic_mime_types, true );
+}
diff --git a/src/wp-includes/media.php b/src/wp-includes/media.php
index 56389c5e1450f..8d1125cecac3b 100644
--- a/src/wp-includes/media.php
+++ b/src/wp-includes/media.php
@@ -5627,9 +5627,7 @@ function wp_show_heic_upload_error( $plupload_settings ) {
  */
 function wp_getimagesize( $filename, ?array &$image_info = null ) {
 	// Don't silence errors when in debug mode, unless running unit tests.
-	if ( defined( 'WP_DEBUG' ) && WP_DEBUG
-		&& ! defined( 'WP_RUN_CORE_TESTS' )
-	) {
+	if ( defined( 'WP_DEBUG' ) && WP_DEBUG && ! defined( 'WP_RUN_CORE_TESTS' ) ) {
 		if ( 2 === func_num_args() ) {
 			$info = getimagesize( $filename, $image_info );
 		} else {
@@ -5660,11 +5658,18 @@ function wp_getimagesize( $filename, ?array &$image_info = null ) {
 		return $info;
 	}
 
+	$image_mime_type = wp_get_image_mime( $filename );
+
+	// Not an image?
+	if ( false === $image_mime_type ) {
+		return false;
+	}
+
 	/*
 	 * For PHP versions that don't support WebP images,
 	 * extract the image size info from the file headers.
 	 */
-	if ( 'image/webp' === wp_get_image_mime( $filename ) ) {
+	if ( 'image/webp' === $image_mime_type ) {
 		$webp_info = wp_get_webp_info( $filename );
 		$width     = $webp_info['width'];
 		$height    = $webp_info['height'];
@@ -5686,7 +5691,7 @@ function wp_getimagesize( $filename, ?array &$image_info = null ) {
 	}
 
 	// For PHP versions that don't support AVIF images, extract the image size info from the file headers.
-	if ( 'image/avif' === wp_get_image_mime( $filename ) ) {
+	if ( 'image/avif' === $image_mime_type ) {
 		$avif_info = wp_get_avif_info( $filename );
 
 		$width  = $avif_info['width'];
@@ -5709,11 +5714,13 @@ function wp_getimagesize( $filename, ?array &$image_info = null ) {
 	}
 
 	// For PHP versions that don't support HEIC images, extract the size info using Imagick when available.
-	if ( 'image/heic' === wp_get_image_mime( $filename ) ) {
+	if ( wp_is_heic_image_mime_type( $image_mime_type ) ) {
 		$editor = wp_get_image_editor( $filename );
+
 		if ( is_wp_error( $editor ) ) {
 			return false;
 		}
+
 		// If the editor for HEICs is Imagick, use it to get the image size.
 		if ( $editor instanceof WP_Image_Editor_Imagick ) {
 			$size = $editor->get_size();