test

snippets/product-media-gallery.liquid

@@ -253,7 +253,8 @@
             id="Slide-Thumbnails-{{ section.id }}-0{{ id_append }}"
             class="thumbnail-list__item slider__slide{% if section.settings.hide_variants and variant_images contains featured_media.src %} thumbnail-list_item--variant{% endif %}"
             data-target="{{ section.id }}-{{ featured_media.id }}"
-            data-media-position="{{ media_index }}">
+            data-media-position="{{ media_index }}"
+            thumbnail-alt={{ media.alt }}>
             {%- capture thumbnail_id -%}
               Thumbnail-{{ section.id }}-0{{ id_append }}
             {%- endcapture -%}