What is no 1 twitter?

As an AI language model, I do not have access to current data but I can give you some generic information.

Twitter is a popular social media platform that allows users to post short messages or updates known as "tweets". The platform was launched in 2006, and as of 2021, it has over 330 million active users worldwide.

There is no official "no 1 Twitter", as the platform is used by many different individuals and organizations for various purposes. However, some of the most popular Twitter accounts include those belonging to celebrities, politicians, and news outlets. The most followed account on Twitter is currently that of the former U.S. president Barack Obama, with over 129 million followers.