Can I delete old categories?
If you have categories that you are no longer using, you can delete them if you want to.
First, have a look in your WordPress dashboard to find out if you have any categories with no posts assigned to them. To do this, hover over Posts in the left panel and then select Categories from the submenu.
You will see a page that's similar to the screenshot below.
Click the "count" button to order by the number of posts in each category. Any with 0 will be at the top of the list.
WordPress automatically creates a page for each category, and it might be worthwhile setting up a 301 redirect for the categories that you delete, if you have a very similar category. For example, if you are deleting the categories "pizza" and "pasta" but you have a category called "Italian", it would make sense to redirect those.
But if you are deleting a category called "Africa" because you have no posts about Africa, it's best practice to not redirect that page. A 410 "content deleted" page will appear -- which is exactly the right thing to happen.
If you do set up a redirect and later decide to add the same category back, it's important to remember to remove the redirect!
We can set up these redirects at a server level for you. As you remove categories, make a list the names of each category you delete, then send it to firstname.lastname@example.org so we can set up the redirects for you.