Roblox also announced it planned to simplify descriptions for content on the platform.
It is replacing age recommendations for certain games and experiences to “content labels” that simply outline the nature of the game.
It said this meant parents could make decisions based on the maturity of their child, rather than their age.
These range from “minimal”, potentially including occasional mild violence or fear, to “restricted” – potentially containing more mature content such as strong violence, language or lots of realistic blood.
By default, Roblox users under the age of nine will only be able to access “minimal” or “mild” experiences – but parents can allow them to play “moderate” games by giving consent.
But users cannot access “restricted” games until they are at least 17-years-old and have used the platform’s tools to verify their age.
It follows an announcement in November that Roblox would be barring under-13s from “social hangouts”, where players can communicate with each other using text or voice messages, from Monday.
It also told developers that from 3 December, Roblox game creators would need to specify whether their games are suitable for children and block games for under-13s that do not provide this information.
The changes come as platforms accessed and used by children in the UK prepare to meet new rules around illegal and harmful material on their platforms under the Online Safety Act.
Ofcom, the UK watchdog enforcing the law, has warned that companies will face punishments if they fail to keep children safe on their platforms.
It will publish its codes of practice for companies to abide by in December.