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.

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

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.

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.

The government on Friday concluded its main arguments in the case -- US et al. v. Google -- and the internet giant started mounting its defense. The case, filed last year, accuses Google of building a monopoly over the technology that places ads on websites around the internet.