A loyalty card does something technically powerful every time it saves fifty cents on soup.
It identifies the transaction.
Without a loyalty account, a receipt may describe an anonymous basket of groceries.
Add a rewards number, phone number, app account, or other persistent identifier and the same basket can become part of a continuing purchase history.
Then the interesting part begins: that retail identity can be linked to the customer’s online identity too.
Kroger describes the connection directly
Kroger’s current privacy notice, updated September 9, 2026, says that when a customer enters a rewards number or alternate ID, purchase information can be associated with the customer or household. The company also says it may link information from multiple sources, including associating in-store shopping activity with website and mobile-app activity and linking device IDs to an account.
See Kroger’s current privacy notice and its explanation of how information is collected.
Kroger also says purchase history may be used for purchase-based advertising and that information may be shared with marketing partners to personalize advertising. See How We Share Information.
That is not a hidden accusation. It is the company’s own disclosed data model.
The reward number becomes a join key
Imagine one customer does all of the following:
- scans a loyalty card in a physical store,
- clips a digital coupon in the app,
- searches for a product on the website,
- buys that product in-store,
- opens a promotional email,
- logs into the same account from a phone.
Each event can be stored separately.
The account makes it possible to connect them.
That combined profile is more informative than the original rewards transaction because it describes both what the person bought and what they considered before buying it.
Target’s current privacy policy describes a similar general idea: it says the company may link or merge interactions across its website, mobile app, stores, online ads, and emails to provide a personalized experience across channels. See Target’s privacy policy.
Loyalty is not secretly surveillance by definition
Rewards programs provide real benefits. Discounts, fuel points, personalized coupons, digital receipts, easier returns, and account history are useful to customers.
The important research question is not whether loyalty programs are inherently bad.
It is how much identity stitching is necessary for the promised benefit, what additional uses are disclosed, and what controls exist over advertising or sharing.
This also separates DIT-367 from the earlier article about loyalty programs generating recurring promotional messages.
Here the issue is not how often the company contacts you.
It is how many different parts of your behavior the loyalty identity can connect.
The Surveillance Economy loves a stable join key.
Sometimes that key is a cookie.
Sometimes it is the phone number you typed at the grocery-store register.