Board Thread:Support Requests - Designing Your Wiki/@comment-45634567-20200520064211/@comment-9605025-20200520213139

Since Fandyllic didn't say what a private wiki is, I am going to mention it just to make sure everyone understands. Whether or not a wiki is considered private has nothing to do with the topic of the wiki. What the term pertains to is whether or not the wiki is open to editing. Wikis that requires users to be on a whitelist in order to edit are considered private wikis. If can be a wiki about a country and still be considered a private wiki if editing is restricted. It can be an wiki on a personal fanfic and won't be considered a private wiki as long as other users are allowed to edit.

As for personal test wikis, they are definitely allowed. In fact, it is one of the options you can select when asked to justify why an apparently overlapping wiki is not a suitable choice for your content.