No One Under Eighteen on Facebook

What it signals here

reaction meaning

Used in comments on videos or posts containing adult humor, mature themes, or explicit political content as a warning to other users.

comment use

Older users may post it genuinely to flag content they find inappropriate or to warn others about adult-only material.

boomer interpretation

Often interpreted literally as a warning label — boomers may use it sincerely to flag content they deem inappropriate for younger family members.

group use

Used in group rules or pinned posts by admins of adult interest groups (humor, politics, lifestyle) to mark group content level.

See it elsewhere