The following categories exist on the wiki, and may or may not be unused. Also see wanted categories.
- Brewster Kahle (1 member)
- Bricklaying (2 members)
- Brindabellas (1 member)
- Broodiness (2 members)
- Bugs (4 members)
- Building (2 members)
- Bus stops (1 member)
- By the Ionian Sea (1 member)
- C.F. Barker Archives (2 members)
- CLI (1 member)
- CSV (3 members)
- Category:Cafés (0 members)
- Cafés (11 members)
- Calendar (2 members)
- Calendars (1 member)
- Camping (2 members)
- Canberra (22 members)
- Captains Lane (2 members)
- Cargo (0 members)
- Carnival (2 members)
- Carrington Street (4 members)
- Cars (4 members)
- Cartography (1 member)
- Casio (2 members)
- Catalogues (1 member)
- Cataloguing (2 members)
- Categories (33 members)
- Categorisation (2 members)
- Cats (0 members)
- Causes (1 member)
- Centenary Building (2 members)
- Changes (1 member)
- Chicago Manual of Style (2 members)
- Chickens (5 members)
- Childhood (1 member)
- Chronology (5 members)
- City of Fremantle (1 member)
- Clare Davies (1 member)
- Climate change (2 members)
- Clontarf Road (2 members)
- Closeness (2 members)
- Clothing (1 member)
- Cloud storage (3 members)
- Cmd (2 members)
- Co-op (2 members)
- Co-operative (2 members)
- Cockburn (1 member)
- Code (6 members)
- Code projects (1 member)
- Code snippets (2 members)