And no product was more dominant than Microsoft's web browser, Internet Explorer. The company's browser was the gateway to the internet for about 95 percent of users in the early 2000s, which helped land Microsoft at the center of a major government effort to break up the company.
Almost two decades later, Google's Chrome now reigns as the biggest browser on the block, and the company is facing challenges similar to Microsoft's from competitors, as well as government scrutiny.
But Google faces a new wrinkle — a growing realization among consumers that their every digital move is tracked.
"I think Cambridge Analytica acted as a catalyst to get people aware that their data could be used in ways they didn't expect," said Peter Dolanjski, the product lead for Mozilla's Firefox web browser, referring to the scandal in which a political consulting firm obtained data on millions of Facebook users and their friends.
And in something of a poetic role reversal, Microsoft is positioning itself to pick up the slack from people who may be fed up with Google's Chrome browser and its questionable privacy practices. Microsoft is expected to release an overhaul of its latest browser, called Edge, in the coming months.
"If you look at anybody who's in a position to strike back and gain market share, it would be Microsoft," said David Smith, a vice president at the market analysis firm Gartner.
Microsoft is just one of a number of companies and organizations looking to take a piece out of Google — some using the company's own open-source software. One name that might be familiar to most consumers — Mozilla's Firefox browser — is also a veteran of the "browser wars" of two decades ago. The nonprofit Mozilla, which has been biting at the heels of leading browsers for most of its existence, is introducing more aggressive privacy settings to try to stand out and take advantage of the privacy stumbles by Google and other tech giants.
The early browser wars took place on desktop computers, before the introduction of smartphones, but the latest fight is more complicated, involving both desktop and mobile applications, and there are a lot of players.
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Web browsers, being the primary way the vast majority of people experience the internet, are a crucial choke point in the digital ecosystem. While the browsers are free to users, the companies that operate them can have an outsized impact on how the internet works — especially if they gain a dominant market position. For a company like Google, which makes most of its money from online advertising, that has meant being able to liberally collect user data.For a nonprofit like Mozilla, more users means the chance to convince developers and other tech companies to adopt their privacy-focused standards.
Smaller browsers like Opera, Brave and Vivaldi have devoted followings, in part because of privacy promises but also because they have a lot in common with Chrome. Google released most of the code behind Chrome as a free, open-source resource called Chromium, a foundation others can use to make browsers with similar functionality.
Last year, Microsoft decided to join the club, saying it would rebuild its Edge browser from the same, open-source Chromium engine, and even make a desktop version for the Mac. Early versions are available for preview.
Microsoft CEO Satya Nadella has talked up the future of the browser, saying at the company's annual developer conference in May that he wanted it to be the "one browser" for people to use "across their work and life" — on desktop computers, tablets and smartphones.
How Microsoft will approach the privacy question is unclear, however. Nadella said he wanted to "push the envelope" by making it transparent to users which cookies are being used to track them — a position far short of what Firefox promises, for example — but the company also says it's in the "early stages of exploring how best to empower users" on the browser.
Meanwhile, Google is facing a deluge of complaints about its size and power — much as Microsoft did two decades ago. The Justice Department is preparing an antitrust investigation of Google, according to The Wall Street Journal, and the company has become a top political target for both Democrats and Republicans.
Chrome, with more than 60 percent market share worldwide, is yet another source of complaints about Google's power, after its search engine and advertisement businesses. Last year, Chrome changed the system for logging in to the browser, a move that one researcher said could allow Google to collect data much more easily.
Firefox trails Microsoft in corporate size and influence, but it is pressing other browsers on privacy and playing up its status as a nonprofit. Last month, Firefox changed the initial settings for new users so that third-party tracking "cookies" such as those used for ad purposes are blocked — meaning the default is no tracking.
Ads don't go away with the change. Instead, they become less personalized and, the thinking goes, less creepy.
Firefox plans to roll out the change to existing users of the browser in the coming months, making it more difficult for advertisers to follow its users around the web. The company is a distant third in the browser market at 5 percent, according to StatCounter.
A technology columnist at the Post wrote in a scathing review last month that he was switching from Chrome to Firefox, calling Google's product "a lot like surveillance software." In a week of desktop websurfing, the columnist, Geoffrey Fowler, wrote that he discovered 11,189 requests for tracker cookies that were blocked by Firefox but would have been allowed by Chrome.
Chrome is planning updates of its own in an effort to give users more reasons to stick with the browser and reassure them about privacy. In May, Google said it would require third-party developers to better label their cookies in a way that Chrome will be able to read and classify, so that users can decide which ones to block.
The browser fight has become heated enough to worry the advertising and media industries. Advertisers have become used to filling up websites with sometimes dozens of "cookies" and other forms of online tracking, and they fear a wider backlash against personalized, data-driven ads.
Last year, the IAB Tech Lab, which works on behalf of the industry to try to set standards for online ads, set up a working group and stepped up direct talks with the makers of web browsers.
"We're working on collaborating with browsers to find solutions that put consumers at the center," Sam Tingleff, the IAB Tech Lab's chief technology officer, said. "We think there's a reasonable middle ground to do so and enable better overall user experiences."
For now, there are few signs that Google's browser dominance will end anytime soon, but the tech industry is riddled with examples of companies that appeared to be invincible just before their fall, including with web browsers.
"It wasn't clear that there was going to be anything that took down Internet Explorer," Smith, of Gartner, said. "But it happened."