The deals didn’t stop on Black Friday. The action has now moved online, where retailers are offering deep discounts.

Cyber Monday is expected to be the largest online shopping day in history, generating a whopping $7.8 billion in sales, an increase of more than 17% from the previous year, according to Adobe Analytics.

Deloitte says shoppers will on average spend $170 more each on Cyber Monday compared to any day of the prior Black Friday weekend.

The sales are especially important for struggling retailers. But with nearly every company spending big on incentives like free shipping, retailers have to be careful not to let discounting harm their bottom line.

The situation is especially dire at Sears (SHLD). The iconic retailer plans to emerge from bankruptcy much smaller and profitable.