How do I give stamps without internet?

The stamp is queued on the device and uploads automatically when the connection returns.

If the internet drops at the counter, you can keep stamping as usual. The stamp isn’t lost: it’s queued on the device, and a bar at the top shows how many stamps are waiting to upload.

Stamp as usual. The bar shows something like: “Offline. 3 stamps waiting to upload.”
Don’t close the browser for good or clear the browser data until the queue is empty.
When the connection returns, the queue uploads by itself and the guests’ cards are updated.

Every queued stamp has its own identifier, so it is never added twice, even if the system retries the upload. The server still checks the per-card limits: if a stamp would exceed the limit, you get a notice during the upload.

Note: While offline you don’t see the latest state of the card, only what the device last knew. That’s why rewards are best redeemed online.

On the guest’s side: the browser card and its QR code appear without internet too, with the last known state, so the guest can show it at the counter.