The new ability will be available to those with a Mojang account through their account page. Those who sign in with their email address are ready to go. Those who don't can migrate their account. Banned players who change their names will remain banned.
Names will remain unique with the new service, and "old unpaid usernames" will be freed up. Players will need to wait 30 days before changing again.
Last September, Microsoft announced its intention to purchase Mojang. Microsoft's $2.5 billion acquisition of Mojang became official in November. In a blog post on the same day as Microsoft's September announcement, Minecraft creator Markus "Notch" Persson announced that he was leaving the company.
"It's not about the money," Persson wrote. "It's about my sanity."