What are “.u” directories, e.g., “category.u”?
Question: I see in my cache directory sub-directories that end in
.u, such as
/category.u/; what are those?
/category/ sub-directory will be for any cache files for your category archive pages (such as
/category.u/ sub-directory is for any user-specific cache files for category archive pages. It sounds like you have Logged-In User caching enabled (WordPress Dashboard → Quick Cache → Plugin Options → Logged-In Users) and this is set to
Yes, and maintain a separate cache for each user.
This means that when a logged-in user visits a category archive page, they will have their own cache files generated in a
/category.u/ directory; the cache filename for the user will be
[user-id] is their WordPress User ID, e.g.,
/category.u/6.html, if their User ID was