Your till should not care whether the internet is up

There is a particular silence that falls over a shop when the till stops working. The queue does not disperse; it just watches.

The trade nobody explains at the demo

Most modern point-of-sale systems are thin clients. The terminal is essentially a browser, and every price lookup, every stock check and every transaction is a round trip to a server somewhere else. When that connection is healthy, this is elegant: one source of truth, instant updates everywhere, nothing to install.

When the connection is not healthy, you cannot sell a newspaper.

What offline-first actually means

An offline-first terminal keeps its own copy of the things it needs to complete a sale: the product catalogue, the current prices, the active promotions and the staff permissions. It writes transactions to local storage first and treats the server as something to reconcile with rather than something to ask permission from.

The hard part is not the storing. It is the reconciliation — deciding what happens when two terminals sold the last unit of something during the same outage. That is a business rule, not a technical one, and it is worth deciding deliberately rather than discovering it at Christmas.

Card payments are a separate question

Worth being precise here: a card terminal usually has its own connection, often mobile. Your POS being offline does not necessarily stop you taking card payments. What it stops is the reconciliation between the sale and the payment — which matters at cash-up, not at the counter.

The practical position

If your business closes when the line drops, that is a design decision somebody made on your behalf. It is worth knowing whether it was made deliberately.