Also called Offline POS
An offline-first POS stores data locally and keeps working without an internet connection, syncing when the connection returns. Billing continues through an outage rather than stopping.
For a shop or a venue where connectivity is unreliable, this is often the single most important requirement. A till that stops when the internet does is not a till.
The trade-off is usually around multi-location reporting and remote access, which are harder when the source of truth lives on a machine in the shop.
Related terms
MinimalPOS handles orders, kitchen, billing and reporting in one flow.