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 than portrayed by the federal government.

The Justice Department and multiple states allege that Google holds a monopoly over online advertising technology, shutting out competitors and charging high fees. Google counters that the government is focusing too narrowly on specific types of ads.

If the DoJ's lawsuit fails, the online ecosystem could worsen for users and third-party companies. Lawyers, nonprofit organizations, and privacy experts recently held a press hearing

A senior Google executive sought to refute the US Justice Department’s antitrust case over its display advertising technology business, testifying that it faces “fierce competition” from the likes of Microsoft Corp.

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 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.