Update: Fastly says it has identified a fix and websites are gradually coming back online.

Due to a major CDN issue, many large websites are currently unavailable. Fastly CDN network appears to be the source of the problem.

Amazon, Reddit, Spotify, and The New York Times are among the sites that are currently experiencing problems. Some websites are completely down, while others are having trouble loading assets such as fonts or images.

A content delivery network (CDN) caches data in regional servers to allow websites to serve content more quickly. Only a few CDNs are capable of handling the traffic demands of large websites, leaving a lot of responsibility in the hands of a small number of centralized server networks.

Failures are uncommon, but when they do occur, they have far-reaching consequences, as we are seeing right now.

Twitter, Spotify, PayPal, eBay, Amazon, and Reddit are among the commercial high-profile web-apps that have been impacted. Other important institutions, such as the UK government’s website, are also affected. So far, it doesn’t appear that Apple relies on Fastly because its services have remained up — Apple’s CDN is primarily provided by Akamai.

According to the Fastly Status page, the company is currently investigating “potential performance impacts with CDN services.”

For the time being, end users will have to wait for upstream issues to be resolved before the sites come back online on their own.