Arbital was envisioned as a successor to Wikipedia. The project was discontinued in 2017, but not before many new features had been built and a substantial amount of writing about AI alignment and mathematics had been published on the website.

If you've tried using Arbital.com the last few years, you might have noticed that it was on its last legs - no ability to register new accounts or log in to existing ones, slow load times (when it loaded at all), etc. Rather than try to keep it afloat, the LessWrong team worked with MIRI to migrate the public Arbital content to LessWrong, as well as a decent chunk of its features. Part of this effort involved a substantial revamp of our wiki/tag pages, as well as the Concepts page. After sign-off[1] from Eliezer, we'll also redirect arbital.com links to the corresponding pages on LessWrong.