Update: Twitter has come back again, about an hour after it went down this morning.
In a statement on its status page, the company said: "The outage was due to an internal configuration change, which we're now fixing.
"Some people may be able to access Twitter again and we're working to make sure Twitter is available to everyone as quickly as possible."
"Thanks for noticing – we're going to fix it up and have things back to normal soon."
Users normally vent on Twitter when any service they use is down but in this case they lacked a space to express their frustration.
There was no indication that any other popular social media sites were down.
A screenshot from Downdetector at 5.20am AEST on Friday.
The company has given no indication of what is causing the outage. Any announcement would normally be on its own platform – but that is down at the moment!
There is no announcement on its Facebook page either.
The latest Facebook post by Twitter is the graphic below. But comments alongside this indicated the frustration of Twitter users.
One, Sachi Virahsawmy, wrote: "I'd love for Twitter to update their Facebook saying that they're down!!"
Another, Denton Hein Bruintjies, commented: "Never knew the day would come so soon that I'd have to come on FB to find out if Twitter is down."
A third, Dave Warburton, wrote: "I’m only here to check if twitter is down for everyone! Usually it’s twitter telling me that Facebook is down."
User Camilo Olmeda commented: "Trump is mad because Twitter is Down and He can't post all his Lies to The World!"
Commenting on the outage, Alex Henthorn-Iwane, vice-president of Product Marketing at network monitoring company ThousandEyes, said: "ThousandEyes tests show no Internet or external network issues from users to Twitter sites. We don’t see any evidence of a volumetric DDoS attack on the Twitter service.
"Rather, like the brief Reddit service disruption this morning, the issue appeared to be server-side as evidenced by HTTP 500 Service Unavailable errors. A ThousandEyes Path Visualisation shows that the network paths from ThousandEyes monitoring agents in various cities to Twitter data centres aren’t seeing any unusual packet loss or other issue."