1. Add Another Store in Plugin Settings
First things first – let’s connect another WooCommerce store in plugin settings, the one you would like to sync the inventory with.
Add a store in plugin settings
If you’re not using WordPress Multisite (or even do not know what that is), it is totally ok. Simple Product Stock Sync works great for any WooCommerce standalone stores.
All you have to do is to go to WooCommerce > Stock Sync in WordPress admin and add a store there. You can see how it works exactly on the screenshot below:

It is not necessary to install the plugin on the second store. But if you would like the second website to sync its product inventory with the first one, then – yes, you have to install the plugin and connect the store in plugin settings as well.
Add a store if you’re using WordPress Multisite
For WordPress Multisite installation the process is slightly different but definitely simpler. Because what the point of using WooCommerce REST API within a WordPress Multisite network when we can save tons of performance using the network functions. Sorry, I just got a little carried away :)
In order to add a store within a WordPress Multisite network you also have to go to plugin settings in WooCommerce > Stock Sync but then all you have to do is to select a store from a dropdown list. That’s pretty much it.

2. How the Plugin Works Exactly?
Now you have configured everything – great!
Probably you already have an idea how the plugin works but let me explain it for you just in a case. The two things that plugin is connected to are Stock quantity and SKU.
You can see both this fields for a simple product below:

And for product variation below:

So, when a product stock quantity has been changed, the plugin will find the product (or product variation) with the same SKU and update its stock quantity automatically.
When a product quantity can be changed:
- Automatically when somebody makes a purchase in your store,
- Manually in product settings,
- Manually when bulk edit products,
- When an order is created manually.
In all these cases the plugin will automatically update the product stock quantity on all the connected stores.