Google's dominance of the search engine market is facing the biggest challenge in its history, but not from a competitor.
Instead it is the US government challenging its dominance.
At the opening of the biggest US antitrust trial this century, the Department of Justice argued Google's dominance of internet search engines has locked out competitors and stifled innovation.
The core of the argument revolves around the simple question, when was the last time you searched for something on the internet without using Google?
Why is the US government taking Google to court?
Kenneth Dintzer, the Justice Department’s lead litigator said at the opening of the trial: "This case is about the future of the internet and whether Google’s search engine will ever face meaningful competition."
Over the next 10 weeks, federal lawyers and state attorneys general will try to prove Google rigged the market in its favour by locking its search engine in as the default choice in a plethora of places and devices.
Top executives at Google and its corporate parent Alphabet Inc as well as those from other powerful technology companies are expected to testify.
The Justice Department filed its antitrust lawsuit against Google nearly three years ago during the Trump administration, charging that the company has used its internet search dominance to gain an unfair advantage against competitors.
Government lawyers allege that Google pays $10bn (£8bn) a year to potential rivals like Apple and Mozilla's Firefox to keep the default search engine on their products as Google.
The US says this disincentivises rivals from investing in a competitive product.
Google Chrome also has a more than 50% market share of the web browser market.
Regulators also charge that Google has illegally rigged the market in its favour by requiring its search engine to be bundled with its Android software for smartphones if the device manufacturers want full access to the Android app store.
"Google’s contracts ensure that rivals cannot match the search quality ad monetisation, especially on phones," Dintzer said.
"Through this feedback loop, this wheel has been turning for more than 12 years. It always turns to Google’s advantage."
Dintzer said that Google strong-armed other companies into giving its search engine a default position as a condition for getting revenue-sharing payments.
"This is not a negotiation," he said, "This is Google saying: Take it or leave it."
He said that Google's anticompetitive tactics prevented Apple from developing a search engine of its own.
Dintzer said the more searches Google processes, the more data it collects – data that can be used to improve future searches and give it an even bigger advantage over its rivals.
This in turn makes its ad optimisation better than any competitor could ever hope.
Dintzer said this is why Google pays so much for its search engine to be the default option on products from Apple and other companies.
US District Judge Amit Mehta likely won't issue a ruling until early next year.
If he decides Google broke the law, another trial will decide what steps should be taken to rein in the California-based company.
What does Google say?
Google counters that it faces a wide range of competition despite commanding about 90% of the internet search market, pointing to Microsoft's Bing and Amazon.
From Google’s perspective, perpetual improvements to its search engine explain why people almost reflexively keep coming back to it, a habit that long ago made "Googling" synonymous with looking things up on the internet.
Off the back of the success of its search engine Google's parent company Alphabet is one of the most valuable businesses on the planet employing almost 200,000 staff.
Most of its £180bn turnover comes from ad sales flowing through a network of digital services anchored by a search engine that fields billions of queries a day.
What could the case mean for Google?
The Justice Department's antitrust case echoes the one it successfully filed against Microsoft in 1998.
Regulators then accused Microsoft of forcing computer makers that relied on its dominant Windows operating system to also feature Microsoft’s Internet Explorer - just as the internet was starting to go mainstream.
That bundling practice crushed competition from the once-popular browser Netscape.
Several members of the Justice Department's team in the Google case - including lead Justice Department litigator Dintzer - also worked on the Microsoft investigation.
Google could be hobbled if the trial ends in concessions that undercut its power. One possibility is that the company could be forced to stop paying Apple and other companies to make Google the default search engine on smartphones and computers.
Or the legal battle could cause Google to lose focus. That’s what happened to Microsoft after its antitrust showdown with the Justice Department. Distracted, the software giant struggled to adapt to the impact of internet search and smartphones.
Google capitalised on that distraction to kickstart its monumental growth.
What could the case mean for the internet?
Although several businesses have tried, most notably Microsoft's Bing, no company has ever posed a real threat to Google's dominance.
Google dominates the search market it so heavily it effectively controls the results people find when looking for something on the entire planet.
Although it has faced some criticism for what results it presents Google mostly offers a wide variety of results.
Nevertheless, this is extremely powerful.
On top of this, all of the data these searches generate are analysed extensively and used when deciding what adverts people see.
Combine this with data harvested from Gmail, YouTube and Google Maps you can learn an awful lot about a person.
Google uses this data to select adverts people see when using their products.
They also sell products that show highly optimised adverts on other websites.
This means while companies like Facebook do similar things with adverts Google is too dominant in the US's view.
If Google was to be broken up or forced to change its business practices the most apparent change would likely be the introduction of other search engines into the market.
The US government alleges Apple would have entered the market long ago if Google did not effectively pay it not to.
Combining this hobbling of Google with the rapid growth of Artificial Intelligence it could mean the search engine market sees dramatic changes.
Microsoft and Google are already working on using AI to improve search quality even further, a successful antitrust suit could see smaller AI firms entering the market too.
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