Having WordPress themes on your site that you are not using and not “active” can open your site up to security issues. They also unnecessarily take up hosting server space. If you don’t need inactive themes it’s a best practice to remove them. Frankly, I can’t think of a reason to keep them.
Follow the steps below to review and remove unused themes from WordPress. Before doing any WordPress maintenance it is a best practice to run a full backup of your WordPress site.
Be careful if you are using a child theme. Don’t delete the parent theme.