The privacy practices of nine major technology companies, including Amazon (AMZN) Alphabet’s YouTube (GOOG) (GOOGL), and Facebook (FB), are being scrutinized by the Federal Trade Commission.

The FTC voted 4-1 to issue orders on Monday to those three companies, along with ByteDance’s TikTok, online gaming communication company Discord, Reddit, Snap (SNAP), Twitter, (TWTR), and Facebook’s WhatsApp., to hand over wide-ranging data on how they collect, use, and present personal information.

The FTC directed the companies to provide data on their advertising and user engagement practices, and how their practices affect children and teens.

“Despite their central role in our daily lives, the decisions that prominent online platforms make regarding consumers and consumer data remain shrouded in secrecy,” stated a December 4 letter from a bipartisan group of FTC commissioners including Democrat Rohit Chopra, Democrat Rebecca Kelly Slaughter, and Republican Christine Wilson.

That letter added: “Critical questions about business models, algorithms, and data collection and use have gone unanswered. 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.”

Specifically, the agency said it wants information related to how social media and video streaming services collect, use, track, estimate, or derive personal and demographic information, and how the companies determine which ads and content consumers see. The FTC wants to know whether the companies apply algorithms or data analytics to personal information, and the impact of such efforts.

The FTC asked the social media and video streaming services to illustrate, in detail, how they utilize demographic information collected on age, country, and whether a user is of Hispanic, Latino, or Spanish origin. The FTC asked them to share the inputs and methodology for assessing their services’ reach, as well as to identify the top 1,000 most populous attributes that make a user valuable to their platform.

“We’re working, as we always do, to ensure the FTC has the information it needs to understand how Twitter operates its services,” a Twitters spokesperson said Monday.

A spokesperson from Discord told Yahoo Finance that the company takes user privacy very seriously and looks forward to working with the FTC to answer its questions.

“Importantly, there are no ads on Discord,” a spokesperson for the company said in an email. “We make no money from advertising, selling user data to advertisers, or sharing users’ personal information with others. Instead, the company generates its revenue directly from users through a paid subscription service called Nitro.”