Does adding the Croct tag slow down our mobile theme?
I run a small Shopify store and do my own theme edits. Last year I installed a CRO app that added an "anti-flicker" snippet and it held my whole page blank on mobile while its script loaded. Customers told me the site looked broken. I removed it and I have been careful ever since.
Before I add anything new I want to know two things. What does the Croct script tag actually weigh, and does it hide the page while it loads? Most of my orders come from phones so this matters a lot to me
2 answers
There is no anti-flicker snippet involved, which is probably the main thing you want to hear. The blank-page trick you saw is something client-side testing tools add to hide the original content while their script decides what to swap. Croct does not work that way, so there is nothing to hide.
The no-code option is a single script tag:
<script src="https://cdn.croct.io/js/v1/lib/plug.js"></script>The library loads without blanking or hiding anything. Tracking and personalization run alongside the page, not in front of it. For the content requests themselves, the documented figure is end-to-end response times under 90 milliseconds at P95, so even when a slot fetches personalized content the wait is small.
I added it to a Dawn-based theme earlier this year and our Lighthouse mobile score did not move in any direction I could measure.
Thank you, that is exactly what I needed to know. The blank page was my biggest fear. I will try it on a duplicate theme first.
One practical tip to add to Callum's answer: test it on an unpublished copy of your theme before going live, exactly as you said in your reply. Duplicate the theme, add the tag, and browse it on your own phone over mobile data. You will see for yourself that the page renders normally while the library loads in the background. That is the fastest way to rebuild trust after a bad app experience, in my opinion.