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Use one shared QR code when every attendee should open the same arrival instructions or check-in page. Use one code per guest only when the event system can securely match that code to a specific registration and staff have a fallback for failed scans. A QR image alone does not verify identity.
Start with the admission question
One shared QR code fits a shared task: opening arrival directions, a venue map, or a general self-check-in page. One code per guest is justified only when the registration system can match that value to a booking and the organiser has a policy for copied screenshots, duplicate scans, and exceptions. A visible square is not identity proof. For a 300-person conference, a shared sign can reduce ‘where do I go?’ questions without pretending that it controls entry.
Lay out the two-lane arrival test
With two entrance lanes, assign one staff member to scan or observe arrivals and one to resolve exceptions. Before doors open, test ten registrations: valid guest, already checked in, cancelled guest, name mismatch, dead battery, no network, and a copied image. Time the fallback path as well as the successful scan. If the exception desk takes three minutes per person, five failures can create a queue even when the QR code itself works. Put the desk location and a human-readable contact point on the arrival sign.
Decide whether a guest code carries risk
A conference badge that merely records attendance has a different risk from a controlled venue or a paid admission. Do not encode a raw name, email address, payment data, or reusable secret into a public-looking QR image. Use the event system’s approved token design and expiration rules where individual codes are needed. Staff should compare the system result with the admission policy rather than accepting a green screen as a universal credential.
Label the shared sign accurately
‘Scan for check-in instructions’ tells an attendee what a shared sign does. ‘Entry pass’ is misleading if the scan only opens a webpage. Place the sign before the decision point, not after a queue barrier, and include a printed URL for someone whose phone cannot scan. A sign that sends people to a generic event homepage creates a second search task at the entrance; the first screen should name the event, date, desk, and next action.
Investigate failures by category
A failure may be physical—small modules, glare, or a damaged badge—or operational—expired registration, missing network, wrong account, or duplicate attendance. Decode a test image to confirm the stored value, then inspect the registration record separately. Do not solve every failure by generating a new code; that can destroy the audit trail. Record the count and reason for exceptions so the next event can improve staffing, signage, token rules, or connectivity.
Keep the code in its proper role
A check-in code is not a safety credential, payment token, or guarantee that every attendee has a compatible phone. NIST identity guidance is published by NIST SP 800-63-4 Digital Identity Guidelines at https://pages.nist.gov/800-63-4/. A QR code does not make a person authorised, safe, paid, or present at an event. Use it to accelerate an explicitly designed check-in workflow with a staffed alternative.
Set a queue budget before doors open
For a 300-person conference arriving over 30 minutes, two lanes must handle an average of 5 people per minute each. Run ten test registrations through both lanes and time the ordinary and exception paths separately. If a normal self-check takes 15 seconds but a cancelled registration takes 3 minutes, route exceptions to a clearly marked desk instead of allowing them to stop the scan lane. Count the test cases: valid, duplicate, cancelled, name mismatch, no battery, no signal and copied screenshot. The code design is accepted only when the fallback keeps the arrival flow moving and staff know who may make an admission decision.
Treat a green screen as an input, not a verdict
A guest-specific token may return a green result because it was previously copied, because it was already scanned, or because the device is displaying a cached screen. Staff must use the registration system and the event policy to decide what the result means. Record the token or booking reference only in the approved system; do not print names, email addresses or payment details in a QR image that can be photographed in a queue. A shared sign should never claim to be an entry credential when it merely opens directions. Its label and its first screen must describe the narrower job: find the desk, retrieve a booking or begin a self-check-in process.
Close the attendance record after the rush
After the first 30 minutes, compare the system's attendance count with the manual exception log. For example, 242 ordinary check-ins plus 11 desk resolutions and 7 unresolved records is more useful than reporting 260 scans. Investigate unresolved cases while staff can still see the person, then preserve the reason codes for the next event: duplicate, no registration, accessibility support, device failure or network failure. Do not regenerate individual codes during the rush unless the registration system records the replacement relationship. Otherwise a later audit cannot distinguish a genuinely new token from a copied or abandoned one.
Prepare a no-network decision
Write the fallback on paper before the event: who can verify a name against an offline list, who can issue a temporary badge, what evidence is recorded and who resolves a disputed admission. Test the procedure with one device in airplane mode. If the entire entry policy depends on a live QR result, a local network outage turns a convenience feature into a queue. A shared instruction sign can still direct guests to the desk, while a guest-specific code becomes one input to the staff decision. Record the outage and later reconcile temporary entries with the registration system.
Brief staff in the language of the sign
If the sign says ‘scan for arrival instructions’, staff should know that it is not an entry pass. Matching the spoken instruction to the route prevents an attendee from being sent between two queues.
Name the exception desk
Put the exception-desk location in the arrival message and on the sign. A guest with no battery should not wait in the scan lane merely to learn where a person can help. NIST SP 800-63-4 Digital Identity Guidelines is the named source for the current external rule or product behaviour.