It is totally natural to have differences between Shopify Analytics and Google Analytics. However, 50% on sessions seems a little odd.
I firstly doubt you have a problem with your Google Analytics integration. Are you using the native Google Universal Analytics integration? You can visit your website and check the real-time data. It can be useful to check if you are seeing one page-view or more. Also, check the e-commerce reports and orders. How is the accuracy there? Do you see all your orders in Google Analytics properly? Is it also double?
Another reason could be some apps (like GDPR or tracking apps) might be blocking your Shopify Analytics from working properly. Do you use any 3rd party app that can do this?
Is the problem only for one day? What data do you see when check last week and the whole week?
There is next to nothing you can do about Shopify sessions reporting. So, our first approach to solving such problems for clients is to audit Google Analytics and correct all issues. At the same time, build out more comprehensive ways to capture more data. I have compiled an audit checklist that you can use to audit your Shopify Google Analytics that we follow to eliminate the most likely reasons for wrong GA data.
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