Google has monopolized the technology used to buy and sell online display ads by restricting or eliminating the choices of its customers — both website publishers and advertisers — the US Justice Department alleged at a federal antitrust trial.

The antitrust trial over allegedly monopolistic practices in the $200 billion digital advertising industry could lead to significant changes.

As the government wraps up its case, it has built a picture of how Google has become dominant among companies that buy and sell ads online.

Google has opened its defense against allegations that it holds an illegal monopoly on online advertising technology with witness testimony saying the industry is vastly more complex and competitive t

Lawyers for the government have revealed damning Google correspondence and called witnesses who describe anti-competitive practices. Google, however, says ‘there is no monopoly power.’