Magento Open Source 2.2.x
Cart Sidebar

The Cart Sidebar is often called the “mini cart,” and displays a summary of the items in the cart. It is enabled by default, and appears when you click the number of items in the Cart Link.

Shopping Cart Sidebar

To configure the mini cart:

1. On the Admin sidebar, tap Stores. Then under Settings, choose Configuration.
2. In the panel on the left under Sales, choose Checkout.
3. Expand the Shopping Cart Sidebar section. Then, do the following:
a. Set Display Shopping Cart Sidebar to your preference.
b. In the Maximum Display Recently Added Item(s) field, enter the maximum number of recently added items that you want to appear in the mini cart.
4. When complete, tap Save Config.