The Federal Trade Commission ordered TikTok, Snap, YouTube, Amazon and Twitter, along with four other social media and streaming sites to turn over information about how they collect and use information about users.

The far-reaching probe is aimed at exposing the algorithms and other tools that have fueled the technology companies' growth and helped them penetrate so deeply into the American psyche.

"Policymakers and the public are in the dark about what social media and video streaming services do to capture and sell users' data and attention. It is alarming that we still know so little about companies that know so much about us," three Federal Trade Commissioner said in a joint statement.

Discord, Facebook, Reddit and WhatsApp were also named in the order.

In launching the probe, the three said it "will lift the hood on the social media and video streaming firms." These social media companies, they argue, turned from a force to connect people to one that is monetizing Americans' private lives for their own financial gain.

The orders were issued under a provision of the Federal Trade Commission Act, Section 6(b), that gives the commission authority to conduct wide-ranging studies that don't have "a specific law enforcement purpose."

The companies have 45 days to respond.

Neither TikTok, which is based in Los Angeles and owned by China-based ByteDance, nor Santa Monica-based Snap responded to a request for comment.

The orders come as big tech companies are under increasing scrutiny from policymakers.

The FTC slapped Facebook with an antitrust lawsuit last month that accused the social media giant of gobbling up rivals like Instagram to weaken competition. And in October, the Department of Justice brought a civil case against Google, accusing the tech giant of having an illegal monopoly on search functionality and its associated advertising.

"We have reached a point of maturity or sophistication and usage where it's time for the government to ask questions about what information is being collected and how it's being used," said Karen North, a former official at the White House Office of Science and Technology Policy during the Clinton administration. "Knowing there is so much information that's been collected, the question becomes how is it being used to manipulate people and is there the kind of transparency demanded by regulation of traditional media."