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How QR code attendance works
A screen shows a code that changes every thirty seconds, people scan it with the camera they already have, and the server decides what counts.
A screen by the door shows a QR code. People point a phone camera at it, a page opens in the browser, and one button records the check-in. The code changes every thirty seconds, and the server — not the phone — decides whether a scan counts.
That last part is what separates a QR attendance system from a printed sign.
Why the code changes
A code that never changes is a photograph. Somebody takes a picture on Monday and checks in from the car park for the rest of the year.
LiteEntry generates a fresh one for each window, signs it, and carries the window it belongs to inside the code. A scan from an old window is refused. You can watch this in the demo: there is a control that hands you a code from a minute ago, and it is turned away.
A photographed code still works for exactly as long as the window plus its grace period — thirty seconds plus two minutes by default, both adjustable per location. That is a real limit rather than a loophole: some tolerance is necessary, because a code that expires the instant it leaves the screen fails honest people whose phone was slow.
What the screen can be
Any device with a browser and a modern camera-capable phone at the other end: a spare tablet, an old phone, a TV, a laptop nobody uses. It needs power, a network and a browser pointed at its display page. There is no terminal to buy, no badge reader, and no per-device licence.
If the screen stops reporting, LiteEntry says so — Live shows that check-ins are impossible at that location, so an empty list there does not read as an empty building.
What happens between the scan and the record
- The camera opens the link, which carries the signed code
- The person signs in with the Google account they already have, once, on that phone
- The server checks the signature, the window, and whichever checks that location enforces
- One button — In or Out, decided by what they did last
- The row appears in the report, on that location’s business day
Nothing runs in the background at any point, and nothing is recorded between check-ins.
Why the server decides
The record is confirmed at the door, not assembled later from what a phone remembered. The time on every row is LiteEntry’s, in UTC — the phone’s clock plays no part, so a device with its date wound back records the same minute as one without.
See how a check-in works for the mechanics, or set one up — it takes about five minutes and ends with you scanning your own screen.
Still stuck? Try the demo — most questions here are quicker to answer by pressing the thing than by reading about it.