The Information Commissioner’s Office (ICO) said the online platform had failed to apply a robust age assurance mechanism to prevent under-13s from creating accounts.

Reddit was therefore processing the personal information of children under the age of 13 without a lawful basis, it concluded.

The ICO investigation also found that Reddit failed to carry out a data protection impact assessment (DPIA) to assess and mitigate risks to children before January 2025.

In July 2025, Reddit introduced new age assurance measures that include age verification to access mature content and asking users to declare their age when opening an account.

John Edwards, the UK information commissioner, said: “It’s concerning that a company the size of Reddit failed in its legal duty to protect the personal information of UK children.

“Children under 13 had their personal information collected and used in ways they could not understand, consent to or control. That left them potentially exposed to content they should not have seen. This is unacceptable and has resulted in today’s fine.

“Let me be clear. Companies operating online services likely to be accessed by children have a responsibility to protect those children by ensuring they’re not exposed to risks through the way their data is used. To do this, they need to be confident they know the age of their users and have appropriate, effective age assurance measures in place.

“Reddit failed to meet these expectations. They must do better and we are continuing to consider the age assurance controls now implemented by the platform.

“Relying on users to declare their age themselves is not enough when children may be at risk and we are focusing now on companies that are primarily using this method. I therefore strongly encourage industry to take note, reflect on their practices and urgently make any necessary improvements to their platforms.”