About
About Dupe Detective
Dupe Detective is a receipt scanner app for iPhone and Mac that finds items you were charged for twice. It's built for grocery shoppers who want to catch checkout mistakes and get them fixed before they leave the store.
What Dupe Detective does
Checkout mistakes are easy to miss, and a long grocery receipt is hard to check by eye. You take a photo of your paper receipt, or import a digital one. Dupe Detective reads every line item on your iPhone and highlights anything that appears more than once. You walk to customer service with the flagged line in hand instead of finding the mistake at home a week later.
What makes Dupe Detective different
- It runs on your phone. Receipts are read with on-device text recognition. There are no cloud servers involved, and scanning works without an internet connection.
- It checks the whole receipt in seconds. You don't have to read 40 lines yourself. Repeated and near-identical items are flagged automatically.
- It works at the stores you already shop at. Costco, Kroger, Fry's, Sam's Club, Walmart and most major grocery stores.
- It costs less than one double-scanned item. The app is free to download, your first 3 scans are free, and then you get a 7-day free trial. After that, Dupe Detective Pro is $4.99 a year for unlimited scanning.
- It does more than scan. Plan your grocery list on your Mac and it syncs to your iPhone through your Apple ID. While you shop, the list scrolls across the top of the app like a stock ticker. Your receipt history stays in the app for returns, warranties and spotting price changes.
Who uses Dupe Detective
- Warehouse club members at Costco and Sam's Club, where receipts run long and items are expensive.
- Families doing a weekly grocery run with full carts and kids in tow, when nobody has time to read the receipt.
- Budget-focused shoppers who track every dollar and want proof when a total looks too high.
- Anyone who has found a double charge after the fact and doesn't want to dispute one with their bank again.
They all use it for the same job: checking the receipt before leaving the store, while a mistake can still be fixed at the counter.
The team behind Dupe Detective
Marcus Chaffee is the founder and developer of Dupe Detective. He designs and builds the iPhone and Mac apps. You can reach him at [email protected].
He built Dupe Detective after one too many trips of standing outside the store, reading down a long receipt line by line to see whether anything had been scanned twice. On a short receipt that works. On a long one it's nearly impossible to catch a repeated item by eye. That frustration became the idea for the app: let your phone check every line in seconds, so you know before you leave.
Research
How often do stores actually overcharge at the register? We collected the most recent government inspections and surveys in one place. Read our checkout overcharge statistics for 2026.