Dozens of websites and apps have been knocked offline.
Amazon's AWS and Microsoft's Azure both experienced faults on Wednesday afternoon, causing websites and apps including Microsoft 365, Outlook, Heathrow Airport, Natwest and Vinted to go down.
Amazon Web Services received a spike of people reporting issues from around 3:30pm according to Downdetector.
The Downdetector website gets network status updates from social media platforms, reports submitted to its website, and other sources around the web.
Microsoft released an update on the Azure issue at 4.35pm where they stated action had been taken to address the issues but are without an ETA.
They said: "Starting at approximately 16:00 UTC, we began experiencing DNS issues resulting in availability degradation of some services.
"Customers may experience issues accessing the Azure Portal. We have taken action that is expected to address the portal access issues here shortly.
"We are actively investigating the underlying issue and additional mitigation actions. More information will be provided within 60 minutes or sooner."
It added: "We are taking two concurrent actions where we are blocking all changes to the AFD services and at the same time rolling back to our last known good state.
"We have failed the portal away from AFD to mitigate the portal access issues. Customers should be able to access the Azure management portal directly.
"We do not have an ETA for when the rollback will be completed, but we will update this communication within 30 minutes or when we have an update."
Dr. Saqib Kakvi, from the the Department of Information Security at Royal Holloway, University of London, told Mail Online: "This is very similar to the AWS outage of last week, which was also a DNS issue.
"Given the scale of these issues and the entities involved, it may be an issue of BGP, which is a protocol that works with DNS to allow the discovery of web services.
"The update at 12:17 p.m. EST stating 'an inadvertent configuration change' may support this, as BGP configuration issues have previously been known to cause such effects.
"Currently, Amazon, Microsoft, and Google have an effective triopoly on cloud services and storage, meaning that an outage of even part of their infrastructure can cripple hundreds, if not thousands, of applications and systems.
"Due to the cost of hosting web content, economic forces lead to consolidation of resources into a few very large players, but it is effectively putting all our eggs in one of three baskets."
