Keep in mind that these services may not work all the time. But being able to see how much a product costs right before the sale starts (and whether the MSRP happened to increase) can be helpful. Putting these tools together can help you deduce whether a deal is worth your money.

WIRED always fact-checks deals to determine their quality. Of course, I'm biased, but you can check out our ongoing deals coverage to find roundups of the best discounts available—during Prime Day and beyond.

What’s a Lightning Deal?

Lightning Deals are limited-time deals that Amazon runs for only a few hours. They're not restricted to Prime Day, but they're especially prevalent during major sales events. Once an item sells out, you may be able to join a wait list, but not always.

Put bluntly, the Lightning Deals selection is often full of impulse buys, like makeup, skin care products, or toys. Prime members can browse upcoming deals on Amazon's website and in the mobile app. The app can also alert you before a Lightning Deal begins. We'll share some of our favorite Lightning Deals in a live blog during the event this year.

How Do Invite-Only Deals Work?

The best deals sometimes sell out quickly. To get around this, Amazon launched an invite-only deals program during Prime Day. Prime members can request an invitation to purchase items that are ex...