Refund apps like Paribus and Earny claim to help you do that by scouring the internet for lower prices after you've already paid.
They keep track of receipts for online purchases and price match policies. When the app finds a price drop, it automatically requests a refund on your behalf, then deposits the difference back to your card.
But first the apps must have access to your email to look for online purchase receipts.
Both apps say they do not sell your information and only look for receipts, but it's a good idea to open a separate email account specifically for online purchases.
In addition to purchase refunds, Paribus offers to track packages shipped through Fed Ex, UPS and Amazon Prime
Each of those companies have an on-time guarantee and could mean a full or partial refund if they are late.
So what do the apps get out of it?
Paribus recently began offering it's service for free, and is widely available for consumers. Earny is only available through certain banks and credit cards.