The M&S website was down in the early hours of this morning - hours after the retailer revealed it's facing a £300m hit to profits following last month's ransomware attack.
A holding page told customers that they were unable to browse the site.
By around 7am, the website was back online, with M&S telling Sky News: "Our website is open for browsing.
"As we work to get things back to normal for our customers, we are doing some overnight updates."
Online purchases have been suspended since the incident on 22 April, and it may be a couple of weeks before services are partially restored.
M&S recently warned that disruption to its operations could last into July, but chief executive Stuart Machin says the retailer is "on the road to recovery".
It is widely believed the retailer fell victim to Scattered Spider, a hacking group that has also been linked to similar attacks targeting The Co-op and Harrods.
Last week, M&S also admitted personal data belonging to some of its customers has been stolen - but the company stressed this didn't include "usable payment or card details".
Passwords were also not affected, but there are reports that contact details such as names, addresses and phone numbers was taken.
The company's valuation has plunged by more than £1bn as the fallout deepens.
"This incident is a bump in the road, and we will come out of this in better shape, and continue our plan to reshape M&S for customers, colleagues and shareholders," Mr Machin told analysts on Wednesday.
(c) Sky News 2025: M&S website goes down - hours after financial impact of ransomware attack revealed
Phoenix Group plots rebranding under historic Standard Life name
Pressure builds on Reeves as borrowing rises ahead of spending review
Bitcoin hits new high as investor appeal widens
Bonhams-owner Epiris eyes plunge into Merlin aquariums
