For a short time today, the Internet partially crashed. Many websites such as Reddit or Pinterest disappeared completely for a short time. The cause was CDNs. But what is this?

Internet crashed: how can this be?

If you wanted to access websites like BBC, Pinterest, Reddit or the Financial Times today, Tuesday, it did not work at all for a while. All these sites, which at first glance have nothing to do with each other, were suddenly gone.

Media reported how suddenly the Internet “went dark.” Access was not possible for about an hour. So what’s the deal with the fact that virtually the Internet crashed and so many websites from so many different organizations were affected at the same time?

CDNs are the cause of this.

What is a CDN?

CDN is an acronym that stands for Content Delivery Network.

A CDN is a service that allows popular websites to keep copies of their pages closer to their customers. For example: If you call up the Reddit forum from Germany, there’s nothing technically wrong with doing so via the servers there in the USA.

The only thing is that it takes a little longer. And in our digital world, no one wants to wait. Calling up the website can be up to ten times faster with a geographically closer copy.

Now, most people may not notice the difference between 20 milliseconds and 200 milliseconds. But with lots of elaborate graphics, photos and videos on websites, that combined can make quite a tangible difference. And that significantly improves user experience.

That’s exactly what a global CDN network is for.

There are many different CDN providers around the world that enable portals to provide exactly this service. One of those providers is Fastly. Fastly has several customers that use its CDN services, such as BBC and Pinterest.

And that’s exactly why it felt like the Internet crashed today. Because when Fastly’s CDN services went down briefly today, it suddenly affected a great many websites around the world. So it can certainly feel like the Internet is suddenly gone.

Could the Internet go down again?

What exactly caused the outage is still unclear. Since the error was fixed after about an hour, there are most likely no hackers behind it. It may have been a programming error or a problem in Fastly’s infrastructure.

Since Fastly is not the only CDN service provider, it is of course quite possible that websites will crash in rows again in the future.

But of course, CDN providers monitor such incidents as today very closely in order to improve their own systems and avoid such outages. After all, no one really wants the entire Internet to crash.