Check the availability of Minecraft names, look up the name history of Minecraft accounts, view Minecraft skins in 3D, convert UUIDs, and much more. To change your Minecraft username:
Visit account.mojang.com, and log in with your Mojang account email address and password.
Next to your Minecraft profile name, click the link that says "Change".
Enter a new name, and confirm the new name by entering your password again.
Click the "Change name" button.
You can change your Minecraft username once every 30 days.
You can switch back to your old username after 30 days. Everyone else must wait 37 days before they can switch to your old username.