In case you've been living under a rock, TikTok is a short-form video app owned by the Chinese company ByteDance. Launching in 2016, it quickly rose to popularity, eventually becoming one of the most-downloaded apps in the U.S. by 2018.

TikTok is facing a fresh European Union privacy investigation into user data transferred to China. The Irish Data Protection Commission opened the inquiry as a follow up to a previous investigation that ended earlier this year with a 530 million euro ($620 million) fine.

Ireland's powerful Data Protection Commission has opened a new inquiry into TikTok over the storage of European users' data on servers in China, the regulator said on Thursday.

An Irish regulator helping police European Union data privacy said Thursday it had launched an investigation into TikTok over the transfer of European users' personal data to servers in China. The DPC on Thursday said it had been informed by TikTok in April that "limited EEA user data had in fact been stored on servers in China,