Rating system

Anime / Manga

 * A: all ages
 * Y: 7+ / 10+
 * T: 13+
 * OT: 16+
 * M: 18+

CNS ratings

 * A: morally unobjectionable. This has 4 sub-ratings in it:
 * A1: all ages
 * A2: 13+
 * A3: 18+
 * L: most adults would find this unsuitable. This replaced A4 in 2003.
 * O: morally objectionable. This rating replaced the former B (morally offensive in part for all) and C (condemned) ratings in 1978

Fan fiction

 * B: 1-4. This was eventually phased out of the system
 * K: 5+
 * K+: 9+
 * T: 13+
 * M: 16+
 * MA: 18+

Adult fan fiction

 * Adult: equivalent to R
 * Adult+: equivalent to NC17
 * Adult++: equivalent to X. Contains sexual content

Original fan fiction (translated from other systems)

 * G: all ages
 * PG: parental guidance
 * PG13: 13+
 * PG14: 14+
 * PG15: 15+
 * R: 17+
 * M: 17+ only
 * MA: 18+
 * NC17: 18+ only