The POS frontend (= cashier view) was coded in Javascript. Thanks to Javascript, all master data is stored in your browser (e.g: Google Chrome) when opening your POS session. In other words, Odoo sends the needed information (customers, products, taxes, etc.) to your browser when opening your POS session. This information is then accessible even when you lose your Internet connection.

When you lose your Internet connection, a message pops-up to inform you lost your connection. The POS remains operational for basic features (e.g. encoding new orders, computing taxes). Those POS orders will be synchronized when retrieving your Internet connection. The wifi icon displays in red the number of orders that need to be synchronized.

The backend (= Odoo database, when your POS session is closed) needs an Internet connection to work. POS features which depend on the backend will then be accessible when retrieving your Internet connection. For example: generate invoices or synchronize your stock levels.