Major media and government websites, including the White House, New York Times, Reddit and Amazon were temporarily down on Tuesday after being hit by a global outage blamed on a glitch from cloud computing services provider Fastly.
The widespread outages around 1000 GMT also hit the UK government website, CNN and the BBC before resuming services more than an hour later.
"Error 503 Service Unavailable" and "connection failure" messages appeared on several websites, later blamed on a problem at San Francisco-based firm Fastly, which scrambled to restore sites.
The company offers a service to websites around the world to speed up loading time for websites.
It competes with rivals such as Akamai and Cloudflare, which handle hundreds of billions of requests every day, playing a key role in global internet access.
Fastly's clients span the globe, and include Deliveroo, Pinterest and Shazam, with a turnover of $291 million last year alone.
The firm said in a tweet after the outages that "the issue has been identified and a fix has been applied. Customers may experience increased origin load as global services return."
It later confirmed "our global network is coming back online", as service was restored on most sites.
- 'Huge' impact -
A slew of sites around the world were hit, including major media such as The Guardian, the Financial Times, France's Le Monde newspaper, Italy's Corriere delle Serra and Spanish daily El Mundo.
Social and entertainment site Reddit was hit, along with the White House and gov.uk websites plus a number of web pages in the Nordic region and the Swedish social security service Forsakringskassan.
"The impact is huge. It's gone and affected millions of web pages and thousands of companies that rely on their services," Jake Moore, a cybersecurity specialist at ESET, told AFP.
He added that since so few companies offer services similar to Fastly's, any service disruptions can have widespread impact.
"If they go down, then of course we then see lots of companies fall over and panic," he said.
Analyst Corinne Cath-Speth echoed the sentiment.
"Almost all internet websites use content delivery networks and cloud services," said the researcher at the Oxford Internet Institute.
"So when those @fastly services fail or falter -- it has major ramifications for everyone's internet experience," she said on Twitter.
"This in turn--raises major questions about the dangers of (power) consolidation in the cloud market & the unquestioned influence these often invisible actors have over access to information."