Footer Credit Options
All WordPress.com users can choose among several options for the footer credit, from a minimalist WordPress.com logo to text options like “A WordPress.com Website” or “Powered by WordPress.com.”
To find these options, head to My Sites → Customize and select the site you want to change. In the Site Identity section, look for the Footer Credit menu. Choose the option you would like to use — the Customizer will let you preview how each one looks on your site — and select Save & Publish to make the update.

Business Plan Sites
If your site is on our Business plan, you have the option to remove the footer credit altogether.
Other Plans
Sites on any plan other than Business are required to keep the footer credit intact. On those sites, you may choose from one of the alternative wordings or the WordPress icon.
Modifying the style of the footer text with custom CSS — i.e. colors and font size — is allowed as long as the credit stays readable.
Adding to the Credit
Using CSS, you can also add content like a copyright notice to the existing footer. If you would like to do that, you can ask in the CSS Customization forum and Staff or our community volunteers would be happy to help.