What are UPC and EAN barcodes?
UPC and EAN are the standard retail barcodes printed on packaged goods: UPC-A has 12 digits and EAN-13 has 13.
UPC (Universal Product Code) and EAN (European Article Number, now called GTIN-13) are the barcodes on almost every packaged product. Both are issued through GS1, the standards body, and identify a specific product from a specific brand owner. UPC-A is the 12-digit code used mostly in North America; EAN-13 is the 13-digit code used everywhere else. A UPC is really an EAN-13 with a leading zero, so modern scanners read both.
The digits are not random. They start with a company prefix licensed from GS1, then the item number, and end with a check digit calculated from the others, which lets the scanner catch a misread. Short versions exist for small packages: UPC-E and EAN-8. If you make and sell your own packaged products through other retailers, you will need real GS1 numbers.
If you only need barcodes inside your own shop, you do not need GS1 codes. Use your SKU and print it as Code 128, which handles letters and numbers and is read by any standard scanner. Code 128 is the usual choice for shelf labels, bulk bins and items made in-house, while UPC or EAN stays on anything that came from a supplier already barcoded.
In SeroPOS each product in the back office has a barcode type: Code 128, Code 39, EAN-13, EAN-8, UPC-A or UPC-E. Print Labels in the back office prints barcodes on sticker sheets or rolls using the sizes you set in Barcode Settings. At the till a USB or Bluetooth scanner works as a keyboard in the product search, and the phone or tablet camera can scan too.
A gift shop stocks a candle that arrives with UPC 0 12345 67890 5 printed on the box, so it is entered with barcode type UPC-A and that number. The shop's own hand-poured candles have no barcode, so they get SKUs like CDL-LAV-8 and Code 128 labels printed from the back office. One scanner reads both.