Squarify.io will automatically keep inventory counts between 1 Square Location and 1 Shopify Shop in sync. For example, if you sell 2 units of SKU A in Shopify, 2 units will be automatically deducted from Square, and vice versa.
I've been using squarify for the last 6 months and I am very happy with the results. I would highly recommend this to small business owners who are using square and shopify. It is affordable compared to other options on the market too.
keeps inventory in sync like magic