Hi,

Odoo POS works as a browser-based single-page app that runs entirely using JavaScript.

When a POS session is opened online, it preloads necessary data like products, customers, and pricing into the browser.

This data is stored locally using IndexedDB, allowing POS to function without needing constant server access.

Orders created during offline mode are saved locally as unsynced data.

You cannot open a new POS session without internet—only existing sessions continue to work offline.

While offline, all POS operations (adding products, calculating totals, printing receipts) still function normally.

Once internet is restored, the system automatically syncs offline orders back to the Odoo backend.

For more details you can refer the official Odoo 18 documentation: https://www.odoo.com/documentation/18.0/applications/sales/point_of_sale.html

Hope it helps.