Not only has the wait been extremely long, but shoppers have also had to struggle against a crashing website, with some reporting that they were booted out of the supermarket queue as soon as they got to the front.
Posting on Twitter, one customer said: "I logged on at 5.59 (am) to get ready, only to find over 135,000 in the queue already."
By 6.13am, users were posting screenshots that showed the queue was up to 180,000 people.
That figure jumped to more than 287,000 a couple of hours later.
A Tesco spokesperson said: "We're currently seeing a high number of visits to our website and groceries app and some customers are temporarily having difficulty logging on or placing orders.
"We're really sorry about this. There are still slots available for both home delivery and click & collect over the Christmas period and we're working to get things back up and running as quickly as we can. In the meantime, we recommend that customers use our website to place their order."
