YouTube has stopped working for some users.
People are seeing a message reading "500 internal server error", rather than the videos they want to watch.
This is the second round of issues the site has experienced today, following an outage earlier in the morning.
According to Down Detector, the video site went down at 3.22am, then quickly recovered before going down again at 1.26pm.
Users are having issues watching videos, accessing the website and uploading clips.
Others, meanwhile, are saying that they can't access channels, but can open videos and use the site's search functionality.
According to some users, logging out of your account and logging back in again seems to solve the problems.
The issues appear to be affecting people across a number of cities around the world, including London, Berlin, Munich and Vienna at the time of writing.
What exactly has gone wrong with the site isn't yet clear, but such problems aren't entirely uncommon.