How it works
A web pixel starts tracking devices on the first page view. At checkout, five identity signals are checked against your order history. Takes two minutes to set up.
Install from the Shopify App Store
Click install, authorize, done. The checkout extension and web pixel configure themselves. No theme editing, no code.
Runs on Shopify's Checkout Extensions API. The web pixel starts collecting device data on every page view immediately. Nothing is injected into your theme.
The pixel starts tracking before checkout
The moment a visitor lands on your store, the OfferGuard web pixel sets a persistent visitor cookie and collects device signals: screen resolution, timezone, hardware profile. By the time they reach checkout, you already know their device.
This is what catches incognito users. They can clear cookies between sessions, but the hardware fingerprint stays the same. The pixel runs on every page, not just checkout.
Create a rule
Pick the product, variant, or collection you want to protect. Choose which signals to check. Set your threshold.
The free plan gives you one rule with email detection. Enough to see if you have a problem. Sentinel adds all five signals.
Customer hits checkout
When someone adds a protected product to their cart and starts checkout, the checkout extension wakes up. It pulls the pixel data for that visitor and starts checking.
The extension matches the checkout session to the pixel's visitor data. If a protected product is in the cart, it runs. If not, it stays quiet.
Five checks run in parallel
Email gets normalized. Phone gets format-matched. Address gets fuzzy-compared. IP gets checked. Device fingerprint gets matched. All at once, under 50ms.
Gmail dots stripped. Plus aliases removed. Disposable domains blocked. Phone numbers standardized to digits. "123 Main Street Apt 4B" matches "123 Main St #4B". All compared against your order history.
Checkout blocked or allowed
If enough signals match, the checkout is blocked. The customer sees a message like "This product is for new customers only." If they're new, nothing happens.
You write the message. It doesn't accuse anyone. The customer can still buy other products in your store. If OfferGuard isn't confident, it lets the order through.
Everything gets logged
Every checkout decision is saved. You can see which signals fired, what matched, and the confidence level. Orders can be auto-tagged or held for review.
Tags go on the order and customer. Risk assessments show in Shopify admin. Fulfilment can be held automatically for flagged orders.
What this looks like in practice
Four scenarios. Each one uses a different signal to catch the same person.
Gmail alias
BlockedDots and plus alias stripped. Both resolve to [email protected].
Different email, same phone
BlockedEmails are different. Phone numbers normalize to the same digits.
Address variation
BlockedStreet abbreviation and unit format normalized. 96% match.
Incognito + throwaway email
BlockedDisposable email blocked on sight. Device fingerprint matches despite incognito.
The five-signal check
All five run in parallel. Under 50ms total. One decision.
checked in parallel, under 50ms