XCancel is a different website, but they just put up a notice literally a few minutes ago saying that they're also shutting down until they get legal advice. For the past few hours, xcancel had been marginally functional (constantly giving you an error message if you tried more than 2 or 3 searches at a time), but now the website is down altogether.

Twitterwebviewer is still up, but I always preferred nitter and xcancel. And I wouldn't be surprised if twitterwebviewer also goes offline in the next day or two.