Liquid Template Variables - current tags
From Spiffy Stores Knowledge Base
The current_tags of a collection are the tags that have been used to filter the current view of the collection.
current_tags is always returned as an array of tag values. If there aren't any tags, then an empty array is returned.
The array can be tested by
{% unless current_tags == empty %}
...
{% endunless %}
For example, with the URL:
/page /collections/hair_raising_stuff/lime+electric+unforgettable
In this case, current_tags will be ["lime", "electric", "unforgettable"].
There may be additional tags which can be accessed using collection.tags.