On occasion, I have to deliver some bad news. This is one of those cases. And I get this question a lot from students.
Did you create a WordPress.com blog but change your mind about your blog’s URL address (yoursite.wordpress.com)?
Unfortunately, you can’t change your blog address after creating it. You’ll have to create a new WordPress.com site. You can do this using the same account you used (usually your email address serves as your account name). You can have an unlimited number of free WordPress.com blogs under a single login account, and you can always delete a blog that you are no longer using with just a few clicks. As you know, if you’re asking this question, it’s also really easy to create a new blog/website using WordPress.
If you’ve already created a lot of content at one address and plan to change (meaning create a new site), you’ll have to manually recreate all of customization features and content on your blog. That means it’s a good idea to love your blog address before you run with it and start creating lots of awesome custom features and witty, informational posts.