The CEOs of four of America's largest tech firms will testify before U.S. Congress on Wednesday in a hearing that promises a healthy dose of political theater, while also offering a window into the thinking of lawmakers trying to rein in Big Tech.

Facebook's Mark Zuckerberg, Amazon.com's Jeff Bezos, Alphabet-owned Google's Sundar Pichai and Apple's Tim Cook – who together represent about 5 trillion U.S. dollars of the U.S. economy – are set to speak before the House Judiciary Committee's antitrust panel.

Subcommittee Chairman David Cicilline has been looking in to allegations by critics that the companies have hurt competitors and consumers with their business practices and seemingly insatiable appetite for data. 

The CEOs plan to defend themselves by saying they themselves face competition and by pushing back against claims they are dominant, which has led to fears the hearing will bring up little new information to hold the companies accountable in the long term.

The hearing marks the first time the four CEOs have appeared together before lawmakers, and will also be the first-ever appearance of Bezos before Congress.

"The hearing is less about substance and is designed to bring attention to Congressman Cicilline and the work the subcommittee has been doing for the past year," said Jesse Blumenthal, who leads technology and innovation at Stand Together, a group that sides with tech companies that have come under fire from lawmakers and regulators in Washington.

The hearing will also test U.S. lawmakers' ability to ask sharp, pointed questions that reflect an understanding of how Big Tech operates. Previous high-profile hearings involving tech companies have exposed the somewhat limited grasp of Washington politicians of how the internet and technology work.

It will also offer lawmakers from both parties a chance to bring up the topic of content censorship – an increasingly sore point for Republican lawmakers, who have repeatedly complained of anti-conservative bias at Big Tech companies.

A detailed report with antitrust allegations against the four tech platforms and recommendations on how to tame their market power could be released by late summer or early fall by the committee, which has separately amassed 1.3 million documents from the companies, senior committee aides said.