Twitter appears to be experiencing a massive outage. Members of our staff in the US, UK, and Japan cannot access Twitter.com, and the social network's APIs appear to be offline, too: first-party and third-party apps are both unable to send or receive tweets. It's not rare for Twitter's website to experience difficulties (also known as the fail whale), but the entire site is unable to load at this time. It's very rare for the social network's APIs to break, though they appear to be coming and going. If you simply must send a tweet, mobile.twitter.com seems to be loading up just fine, though it's not running at full speed. We've reached out to Twitter to see what the problem is, and we'll update this post when we hear more.
Update: We've received official comment from Twitter: "Users may be experiencing issues accessing Twitter. Our engineers are currently working to resolve the issue.
Update 2: Services look to be coming back up: Twitter.com is loading up and the APIs are working, too. We're waiting to hear from the company what caused today's outage.
Update 3: Despite a brief tease of availability, Twitter.com is down again. We'll let you know if the company provides any additional information about the outage.
Update 4: As of 2:10PM ET, Twitter.com is back up. Good luck to us all.
Update 5: Twitter is certainly having major issues on its end. The site is back down as of 2:50PM ET. We'll update this post when we hear final word from Twitter that everything is back to normal.
Update 6: Details are trickling in on what caused today's massive problems with Twitter — one of the largest ever for the site — and it looks like it was due to a bug.
Today's outage is due to a cascaded bug in one of our infrastructure components. We'll provide updated information soon.— Twitter Comms (@twittercomms) June 21, 2012