Big Tech on trial: Key moments from the historic hearing

The highly anticipated testimony of Amazon boss Jeff Bezos was hit by his broken audio feed for 2 hours.

Later on, however, he answered questions about Amazon's pricing and clarified that they acquire businesses for market position.

On the allegations of using seller data, Bezos said they have the policy to prevent that but "I can't guarantee you that policy has never been violated."

As many expected, Facebook's Mark Zuckerberg was grilled over his company's acquisition of Instagram.

The panel produced his internal emails, calling Instagram 'disruptive' and implying that he wanted to neutralize the competition, among other things.

In his defense, Zuckerberg pointed out that the deal was approved by the FTC at that time, and "it was not a guarantee that Instagram was going to succeed."

Content handling was a major point of discussion, with Republican lawmakers alleging the case of censorship and bias against conservatives, while Democrats accusing failure to censor hate speech.

Zuckerberg, in response, said that Facebook is "one of the companies that defends free expression the most" and that it is no arbiter of truth but also remains focused on weeding out hateful content.

Bias was also among the questions Google's Sundar Pichai faced, with Rep. Gregory Steube, a Florida Republican, claiming that Google's Gmail marked his campaign emails to supporters, including parents, as spam.

"There is nothing in the algorithm that has anything to do with political ideology," Pichai answered, noting that "We do get complaints across the aisle."

Questions even went to Google's defense contracts.

Pichai also faced questions regarding Google's decision to leave US military contracts following employee backlash while still conducting operations in China and benefiting them.

In response, Pichai noted, Google's work in China is "very, very limited" and the company is "deeply committed to supporting the US military and the US government." He added Google was still working with the US government on several contracts.

Tim Cook fielded questions related to Apple's App Store rules, favoring certain developers, and the commission charged from them.

He said App Store rules are transparent and its fee, which is similar to that charged by others, has not increased since the 'feature' debuted years ago.

Cook also said they did reduce commission for some developers (Amazon Prime Video) if they met certain conditions.