The Department of Justice announced Tuesday it has opened formal antitrust investigations into three of the country's largest technology platforms, targeting alleged anti-competitive practices in digital advertising, cloud computing, and app distribution markets. The investigations represent the most sweeping federal action against big tech in years and could lead to significant structural remedies if violations are found. Officials declined to name the companies under investigation, but sources familiar with the matter confirmed the probes involve companies with a combined market capitalization exceeding $6 trillion. Industry groups called the move 'regulatory overreach,' while consumer advocates praised it as long overdue.