The US Federal Trade Commission (FTC) ordered Amazon, Facebook, Google and Twitter to divulge details about how they collect and use personal data, as part of a study to inform the regulator’s privacy stance.

In a joint statement, FTC Commissioners Rohit Chopra, Rebecca Slaughter and Christine Wilson said companies now “follow users everywhere through apps on their always-present mobile devices”, monitoring where they go, what they do and who they socialise with.

The Commissioners argued critical questions about how this information is used had gone “unanswered”, with the study to “shed light on the business practices deeply embedded in our digital lives”.

Information on how companies gather, track, analyse and act on personal and demographic details were sought, along with how they decide which ads and content users see; measure and promote user engagement; and how these practices impact young and teenage children.

Amazon; ByteDance; messaging app Discord; Facebook and its subsidiary WhatsApp; Reddit; Snap; Twitter; and Google subsidiary YouTube were given 45 days to respond.

The FTC employed a law allowing it to conduct “wide-ranging studies that do not have a specific law enforcement purpose” to justify its demands.

Twitter was probed by the FTC earlier this year for allegedly allowing users’ personal information to be used for targeted advertising.

In 2019, the regulator fined Facebook $5 billion for privacy infringements relating to the Cambridge Analytica data breach, and Google $170 million for breaches of child privacy laws by YouTube.