The following categories exist on the wiki, and may or may not be unused. Also see wanted categories.
- 990WikiCharacters (10 members)
- Achievement images (32 members)
- Article management templates (4 members)
- Articles with issues (1 member)
- Audio files (347 members)
- Banners (7 members)
- Candidates for deletion (1 member)
- Candidates for termination (1 member)
- Category of power! (1 member)
- Chaos Insurgency images (4 members)
- Character images (6 members)
- Characters (23 members)
- Class-D images (11 members)
- Community (5 members)
- Containment Breach: Run images (16 members)
- Content (3 members)
- Copyright templates (0 members)
- D-9341 images (3 members)
- Difficulty images (5 members)
- Disambiguations (0 members)
- Document images (59 members)
- Documentation templates (13 members)
- FR Translation (0 members)
- Formatting templates (16 members)
- Foundation (12 members)
- Foundation images (2 members)
- Gameplay Elements (6 members)
- Gate A images (4 members)
- Gate B images (7 members)
- Gifs (5 members)
- Guard images (14 members)
- Help (1 member)
- Helpful (6 members)
- Hidden categories (0 members)
- Hostile (7 members)
- Images (34 members)
- Indev images (6 members)
- Infobox templates (0 members)
- Inventory icons (44 members)
- Item images (1 member)
- Items (10 members)
- Janitor images (2 members)
- Jim Gonzales images (5 members)
- Joke SCP audio (2 members)
- Joke SCP images (5 members)
- Keycard images (7 members)
- Label images (16 members)
- Landscape images (6 members)
- Legal notices (3 members)
- Loading screen images (30 members)