Evan Williams Is Stepping Down as C.E.O. of Medium

Evan Williams, the serial tech entrepreneur who co-founded Twitter, said in a

that he was stepping down as the chief executive of Medium, the company he founded that sought to reinvent publishing on the internet.

Mr. Williams — known as “Ev” in tech circles — said in the post that he was planning to form a company that would allow him to “spend the next few months (or years) learning as much as I can about things I…