If you ever buy something at Walmart, you are being tracked. You might not know just how much they know about you, but they know a surprising amount.

Tracking customers isn't really new for Walmart. The reason they're tracking you has recently expanded. It used to be that they only wanted information about individual customers to specifically target ads to individual customers. They still do this by tracking your purchase history and matching that up with your personal information like your name, phone number, address, and email address that they get from their loyalty programs or your Walmart.com account. They also watch what you're looking at on their website and app, especially the things you buy or put in your wish list. When you walk into their store and connect to their wifi, they analyze how you travel through it and what displays you may have walked by. They pay attention to how you fill out customer surveys and how you view specific brands on social media. They use cameras to see what parts of the store you return to and spend the most time in.

That's a lot of data, and many people are concerned about just how much Walmart knows about them. But now, they're tracking customers for an entirely new reason: shoplifting.

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Walmart has just admitted to using invisible barcodes, specifically for self-checkout stations. The barcodes were developed by a company called Digimarc. They allow items to be scanned much easier and help them eliminate shoplifting.

If the self-checkout thinks you may have slipped an extra item into a bag, it will suspend your transaction and ask a representative to check.

The fear of some customers is that in the name of loss prevention, Walmart could be profiling customers without their knowledge.

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