BarcodeChecker is an app to scan and check event tickets with barcodes or QR codes. It allows event organizers to verify barcode tickets at the entrance with one or multiple Android smartphones and log attendance. You cannot use the app to scan lottery tickets or purchased tickets if you are not the event organizer and have a list of valid barcodes. Each valid ticket is admitted only once; forged or copied tickets are rejected. After scanning a valid barcode the smartphone flashes green and be