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 accuses the Silicon Valley tech firm of engaging in a systematic campaign to seize control of high-tech tools used by publishers, advertisers and brokers to facilitate digital advertising.

Federal Judge Amit P. Mehta sets courtroom schedule for the remedy phase of the Justice Department’s landmark case against the internet giant, having ruled last month that it illegally acts as a monopoly in internet search.

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.

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.

Google opened its defense against allegations that it holds an illegal monopoly on online advertising technology Friday.

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.