Loyalty card barcodes, explained
Behind every card there's a number, and the barcode is just how the till reads it. Knowing which format your card uses helps when something goes wrong.
The most common formats
Most supermarket cards use EAN-13, the same 13-digit code as products. Many fashion and electronics shops use Code 128, which also takes letters. Newer cards, especially inside apps, use a QR code. Kardpal also supports EAN-8, UPC, Code 39, Code 93, Codabar, ITF, Data Matrix, Aztec and PDF417.
The number under the bars
In linear barcodes the number printed under the bars is the content of the code. If the card is worn, typing it into Kardpal is enough: the code is drawn again, identical. In a QR code the content can be long text or a link, so it has to be scanned.
If you type the number
Kardpal picks the format from the length: 13 digits become EAN-13, 8 digits EAN-8, 12 digits UPC-A, everything else Code 128. If the till won't take it, open the card, tap Edit and try the format printed on the card.
Why the till can't read the phone
Older laser scanners read light reflected off a printed card and struggle with screens. Image scanners, the most common today, read phones without trouble. Before giving up, turn the brightness all the way up, avoid reflections and hold the phone still about ten centimetres away.
Screen protectors and cracks
A matte protector or a crack over the code can be enough to confuse the scanner. Kardpal draws the code large on a white background to leave some margin.
When it just won't scan
Under every code Kardpal shows the number in plain text: the cashier can type it in. Almost every till accepts it, because for the system it's the same as scanning the card.
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