Facebook, the world's second most popular site, is unusable to everyone across the world and on every platform.

The social network, which prides itself on never going down, seems to be broken without explanation.

Facebook's error page said that the site was "working on it" and would "get it fixed as soon as we can", though that message appears to be automated.

For some users, the site seemed not to be appearing at all. For others, Facebook's own now slightly old-style error page was brought up when trying to access the site.

Facebook's own "Platform Status" page, which is used to communicate when the site is broken, why and when it will be fixed, also seemed to have been hit by the problem and was inaccessible.