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La Crosse Today
By the People, for the People
The Secret Language of UPC Barcodes Revealed
How those lines on product packaging communicate with scanners to enable fast checkout and inventory tracking
Apr. 10, 2026 at 9:10am
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The hidden geometry and optical engineering behind the humble UPC barcode, an unsung hero of the modern retail economy.La Crosse TodayThe Universal Product Code, commonly known as a barcode, is a product description code designed to be read by a computerized scanner at the cash register. The UPC allows for fast checkout at the point of sale and gives store owners an easy method to monitor inventory. The barcode consists of 12 numbers in groups of 7-5, with the last number serving as a check digit to inform the scanner if there is an error in the other numbers.
Why it matters
The UPC barcode system has become an integral part of modern retail, enabling efficient checkout and inventory management. Understanding how these ubiquitous barcodes work provides insight into the technological infrastructure supporting the consumer economy.
The details
The first number in a UPC code describes the product, while the next five digits identify the manufacturer. The following five numbers describe the product itself, such as size, weight, color, or other distinguishing characteristics. The final number is a check digit used to inform the scanner if there is a mistake in the other numbers. The price is never coded into the bars of the UPC - it is entered into the computer system by the cashier operator. The 'guard bars' in the middle of the UPC allow the barcode to be scanned from left-to-right or right-to-left.
- The first UPC barcode was scanned at Marsh's Supermarket in Troy, Ohio, on June 26, 1974.
- Today, UPC barcodes are a standard feature on nearly all consumer products worldwide.
The players
Marsh's Supermarket
The supermarket in Troy, Ohio, where the first UPC barcode was scanned in 1974.
Smithsonian National Museum of American History
The museum in Washington, D.C. that displays the original pack of Wrigley's gum scanned in that historic first UPC transaction.
The takeaway
The UPC barcode system has become an invisible but essential part of modern retail, streamlining checkout and inventory management. Its widespread adoption demonstrates how new technologies, even ones initially met with skepticism, can become indispensable when they provide clear benefits to businesses and consumers.
