Back in September of 2018, Squarespace decided to no longer allow code / HTML in image titles. Here’s a fix to give you back that functionality. Simply enter this code into SETTINGS > ADVANCED > CODE INJECTION.
If you have AJAX LOADING on your website, disable that first by going to DESIGN > SITE STYLES and unchecking the option for AJAX LOADING (only some of the newer templates have this option so if you’re using an older template, you can ignore this step.)
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.2.2/jquery.min.js"></script>
<script>
$(function(){
$(".image-slide-title").each(function(){
$(this).html($(this).text());
});
});
</script>
P.S. You may have to change “.image-slide-title” depending on how you’re using titles.