Planning to order from online electronics store Newegg? Sorry, but its standard shipping deadline has already passed; still, shoppers have time to make an order eligible for three-day shipping.
Regardless of retailers' stated cutoff dates, online shopping experts have encouraged consumers to place their orders as early as possible, to ensure they receive their packages on time. Last year, wintry weather and record-high package volumes caused many people to get their gifts after Christmas.
Read MoreFingers crossed: Retailers allow late online orders
So far this year, it appears deliveries are running more smoothly. According to data from Slice, a firm that tracks shipments, average delivery speed for the first 18 days of the season, starting Black Friday, was 4.6 days. That compares to 5.4 days over a comparable period last year.
Still, Kevon Hills, vice president of research at StellaService, cautioned that shoppers need to pay close attention to retailers' deadlines because they can shift as the season progresses. Amazon, for example, announced on Tuesday that it extended its free shipping order cutoff to Friday. Prime members can order as late as Monday, three days before Christmas.
Read MoreLast-minute shopper? These store to extend hours
"We certainly expect to see companies move that date around as we get closer to their cutoff," Hills said.
See the infographic below to check more than three dozen retailers' online shopping deadlines as of Tuesday at 9 a.m. Most have been converted to Eastern Standard Time, though some relate to local time.