The Jan. 6 select committee on Thursday subpoenaed Alphabet, Meta, Reddit and Twitter for records as part of its investigation of the Capitol insurrection.

Why it matters: The four social media companies have key information related to the spread of misinformation, efforts to overturn the 2020 election and domestic violent extremism, the panel said.

• Alphabet's YouTube served as a platform for communicating plans of the Jan. 6 attack, including livestreams as it took place, according to the committee.
• Meta's social media platforms, most prominently Facebook, were reportedly used to spread conspiracy theories about the election, coordinate the Stop the Steal movement and share messages of hate and violence.
• A Reddit community named "r/The_Donald" gained traction before migrating in 2020 to the website TheDonald.win, which hosted "significant discussion and planning" for the insurrection, per the committee.
• Twitter was also used to communicate plans and amplify allegations of election fraud, "including by the former President himself," the panel noted in a release. The company was allegedly warned that its users were using the platform to coordinate potential violence ahead of Jan. 6.

The subpoena comes after "inadequate responses" to prior requests for information, the committee said.

What they're saying: "Two key questions for the Select Committee are how the spread of misinformation and violent extremism contributed to the violent attack on our democracy, and what steps — if any — social media companies took to prevent their platforms from being breeding grounds for radicalizing people to violence," committee chair Bennie Thompson (D-Miss.) said in a statement.

• "It’s disappointing that after months of engagement, we still do not have the documents and information necessary to answer those basic questions ... We cannot allow our important work to be delayed any further."

The companies: "We’ve been actively cooperating with the Select Committee since they started their investigation ... and are committed to working with Congress through this process," a Google spokesperson said. "We remain vigilant and are committed to protecting our platforms from abuse."

• "Meta has produced documents to the committee on a schedule committee staff requested — and we will continue to do so," a spokesperson said.
• "We received the subpoena and will continue to work with the committee on their requests," a Reddit spokesperson said.
• Twitter declined to comment.