Hey @Tom2
Welcome to the Klaviyo Community! Thank you for coming to the community to ask your question.
What integration are you using for your site? Klaviyo’s JavaScript onsite tracking is loaded asynchronously. This means it will not block other aspects of your site from loading. However, Google’s PageSpeed Insights and other site speed reports may still flag it as a contributing factor in your site’s load times. However, the more signup forms you have per page the slower the signup forms will load. One thing you can do to try to improve your page load speed by unchecking the automatic injection of the onsite script and Manually Install klaviyo.js for Shopify Stores to your theme.liquid file before the closing </body> tag. Here's your script required for manual installation:
<script async type="text/javascript" src="//static.klaviyo.com/onsite/js/klaviyo.js?company_id=COMPANYID"></script>
Hope this helps! Thank you for being part of the Klaviyo Community!