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# How do offline ticket scanners work?

> Understand cached validation, duplicate-scan risk and reconnect reconciliation for events.

**Offline ticket scanning validates admission credentials using data and rules stored on the scanning device when the network is unavailable.** It can keep entry moving during a connection failure, but its reliability depends on what the device knows before going offline and how conflicting scans are resolved afterwards.

## What must be available locally?

A scanner typically needs authorised credential identifiers or cryptographic verification information, event and session scope, access zones, relevant ticket statuses and an admission log. The precise cache design depends on privacy, scale and whether the ticket uses a static barcode, dynamic credential or NFC.

## Where do offline risks arise?

| Situation                                    | Risk                                                  |
| -------------------------------------------- | ----------------------------------------------------- |
| **Ticket was refunded after last sync**      | Stale device might admit a revoked credential         |
| **Same ticket scanned at two offline gates** | Both may accept without a shared live duplicate check |
| **Scanner lost or stolen**                   | Sensitive data and credentials may be exposed         |
| **Device clock incorrect**                   | Time-based rules may evaluate incorrectly             |
| **Sync fails on reconnection**               | Attendance counts and exceptions remain incomplete    |

Offline support should state its limitations rather than promise perfectly synchronized duplicate prevention without connectivity.

## What happens after reconnection?

Devices upload scan events with timestamps, gate/device identifiers and outcomes. The central system deduplicates and flags conflicts, while preserving the original audit trail. An offline scan accepted at the gate cannot always be physically undone; exception handling must distinguish customer service from historical accounting.

## What should event teams prepare?

Sync admission data before doors, test airplane mode, verify battery/charging and provide a device replacement process. Limit cached personal data; implement device lock, credential expiry and revocation procedures. Coordinate security, ticketing and access teams on what staff should do if a pass is rejected while offline.

**Example:** At a multi-gate venue, two devices isolated from each other may each accept the same screenshot. After sync the platform should show an admission conflict, not erase one scan to make totals appear clean.

## Related explanations

#### [How does venue access control manage restricted zones?](/distribution-access/how-does-venue-access-control-manage-restricted-zones)

Distribution & Access · Entry and access control

#### [How does ticket scanning and validation work at events?](/distribution-access/how-does-ticket-scanning-and-validation-work-at-events)

Distribution & Access · Entry and access control

#### [What is event access control?](/distribution-access/what-is-event-access-control)

Distribution & Access · Entry and access control

#### [How do ticket transfers work?](/distribution-access/how-do-ticket-transfers-work)

Distribution & Access · Transfers and resale

[More in Distribution & Access →](/distribution-access)