Chrome is now the most popular browser across all devices, thanks to Android’s popularity and the rise of Chrome on Windows PCs and Mac computers. As Google continues to dominate our access to the web, information through its search engine, and services like Gmail or YouTube, Chrome is a powerful entry point in the company’s vast toolbox. While Google championed web standards that worked across many different browsers back in the early days of Chrome, more recently its own services often ignore standards and force people to use Chrome.

Chrome, in other words, is being used in the same way that Internet Explorer 6 was back in the day — with web developers primarily optimizing for Chrome and tweaking for rivals later. To understand how we even got to this stage, here’s a little (a lot) of browser history. If you want to know why saying "Chrome is the new Internet Explorer 6" is so damning, you have to know why IE6 was a damnable problem in the early ‘00s.

A brief history of browsers

Microsoft’s PC dominance with Windows peaked 16 years ago. Alongside Intel, Microsoft spent at least $1 billion promoting the release of Windows XP, with a TV commercial featuring Madonna’s Ray of Light. It was an era before the iPod, Gmail, or YouTube, and Microsoft didn’t even have competition from Google at the time. Microsoft acted like a company that could do what it wanted, and it pretty much did. After crushing its Netscape competition, the era of Internet Explorer 6 was born.

Internet Explorer 6 debuted with Windows XP, and was tied closely to many of its features. As XP grew in popularity, so did the web. IE6 arrived just as the “dot com” bubble was collapsing, and internet usage in the US was growing rapidly. For many, Internet Explorer was the primary way of accessing the internet, and the logo became synonymous with the internet. At its peak, Internet Explorer 6 dominated 90 percent of the entire browser market.

Microsoft controlled the way that millions of people accessed the web, and with Internet Explorer 6, it started to flex its muscles. As the web was becoming far more popular, standards were emerging that would help developers build sites and applications that would work across multiple devices and browsers. Internet Explorer 6 largely ignored web standards at the time, and set Microsoft and web developers on a path of painful decisions for years to come.

Ignoring web standards meant that developers started to code their sites around Internet Explorer specifically, and would recommend that their customers only accessed their site through Internet Explorer. Internet Explorer 6 existed for a full five years ignoring web standards and with a number of security flaws, but rivals started to emerge. In 2004, the Mozilla Foundation, founded by former browser maker Netscape, released Firefox 1.0. It introduced tabbed browsing and a pop-up blocker, and fans raised cash to pay for a full-page ad in the New York Times. It was heralded as the Internet Explorer killer, and it was the first serious alternative since Netscape.

Microsoft hit back with Internet Explorer 7 in 2006, adding tabbed browsing and other features that mostly kept people loyal to the Windows default. IE7 didn’t improve Microsoft’s web standards support enough, and criticism over Microsoft ignoring web standards started to grow stronger. Even the creator of the World Wide Web, Tim Berners-Lee, criticized Microsoft’s efforts.

At the time of Firefox’s release, Google was rapidly growing its search and advertising business. Instead of building its own Chrome browser, it was busy creating the Google Toolbar. (Notably, it was one of the very first major projects led by now-CEO Sundar Pichai.) The toolbar was an add-on for Internet Explorer or Firefox that added a pop-up blocker and easy access to Google search. It acted as a Trojan horse to add extra features into browsers, and direct people to Google services. Google promoted it heavily on its search engine pages, and the pop-up blocker was particularly popular with Internet Explorer 6 users.

As Firefox popularity grew and frustrations over Internet Explorer intensified, Google entered the market in 2008 with its own Chrome browser. Google focused on web standards and respected HTML5, passing both the Acid1 and Acid2 tests with the first release of Chrome — something Microsoft had been failing badly at. Developers flocked to Chrome because it enabled them to build better websites based on web standards, and it started a consumer war of market share between Internet Explorer, Firefox, and Chrome.

While Chrome has never managed to capture 90 percent of all desktop browsing market share, it’s now the dominant way people access the internet across devices. Netmarketshare, W3Counter, and StatCounter all place Chrome at around 60 percent of desktop browsing, with Safari, Firefox, IE, and Edge all far behind with up to 14 percent market share each (depending on who you trust). Either way, Chrome now has the type of dominance that Internet Explorer once did, and we’re starting to see Google’s own apps diverge from supporting web standards much in the same way Microsoft did a decade and a half ago.

Works best (or only) with Chrome

Whether you blame Google or the often slow moving World Wide Web Consortium (W3C), the results have been particularly evident throughout 2017. Google has been at the center of a lot of “works best with Chrome” messages we’re starting to see appear on the web. Google Meet, Allo, YouTube TV, Google Earth, and YouTube Studio Beta all block Windows 10’s default browser, Microsoft Edge, from accessing them and they all point users to download Chrome instead. Google Meet, Google Earth, and YouTube TV are also not supported on Firefox with messages to download Chrome. Google has publicly promised to support Earth on Edge and Firefox, and the company is “working to bring YouTube TV to more browsers in the future.”

Hangouts, Inbox, and AdWords 3 were all in the same boat when they first debuted. It’s led to one developer at Microsoft to describe Google’s behavior as a strategic pattern. “When the largest web company in the world blocks out competitors, it smells less like an accident and more like strategy,” said a Microsoft developer in a now-deleted tweet.

Google isn’t alone in its “works best with Chrome” approach either, as other web companies have started to reveal that their websites work best in Chrome. Groupon, Airbnb, and Seamless are all guilty of it, even prompting one Chrome team member to state “please don’t build sites for just Chrome.” It’s a useful piece of advice that Google isn’t putting into practice itself, though. (Groupon later walked back its “Optimized” for Chrome policy with a overly cute Tweet.)

So why is this happening? “Of the dozens of web projects being worked on at any given time at Google, only a small fraction of those require Chrome at some point in their development cycle, primarily due to resource or technology constraints,” explains Ben Galbraith, director of the Chrome Web Platform in a statement to The Verge. “In every case, we work to try to overcome these constraints whenever possible because we believe that an open web is critical to building a better web.”

A lot of this probably comes down to pure engineering resources at Google and other web companies, rather than a conspiracy to crush Firefox or Edge. Google employees use Gmail, Google, and Chrome, and so do most of their customers, so it’s understandable they’d optimize for Chrome. Google’s Chrome team is still a big proponent of the open web, but if the rest of Google is optimizing services for Chrome then it creates this bad look.

“One issue is that Google developers often create many of the new standards, they are extremely active in new feature development for the web,” explains Jason Ormand, a performance engineer at Vox Media. “They write up proposals and get them through the working standards group, W3C, so that they become standards.” That often means Google is the first to ship with these standards, because the company has been advocating for them. Mix that together with a lot of developers using Chrome for web development and the issues are obvious.

It’s hard to imagine this Chrome-only situation getting any better, though. Google moved away from WebKit and towards its Blink rendering engine years ago, and there have been lots of optimizations to open source libraries, frameworks, and other parts of the engine that cause bugs in other browsers. You’ll notice this if you try and use Safari, Firefox, or Edge in certain sites where developers have initially targeted Chrome, and its easier for website support staff to simply recommend downloading Chrome than rewrite parts of their code. Developers have also spent years optimizing for Chrome, and working around some of its quirks with Chrome-only fixes or changes.

Google also controls the most popular site in the world, and it regularly uses it to push Chrome. If you visit Google.com in a non-Chrome browser you’re prompted up to three times if you’d like to download Chrome. Google has also even extended that prompt to take over the entire page at times to really push Chrome in certain regions. Microsoft has been using similar tactics to convince Windows 10 users to stick with Edge.

The troubling part for anyone who’s invested in an open web is that Google is starting to ignore a principle it championed by making its own services Chrome-only — even if it’s only initially. Given the amount of times this has occurred already, the most recent Chrome-only Google app, YouTube TV, isn’t likely to be the last one.

“This is really not acceptable,” says Jen Simmons, a member of the CSS working group and developer advocate at Mozilla, referencing Groupon optimizing its site for Chrome. “Web devs, you can do better. Develop for the web, not one browser. Otherwise you are screwing over your users.”

John Gruber, author of the Daring Fireball blog and inventor of the Markdown publishing format, warns there could be more of this to come. “There is so much Chrome-only stuff right now,” says Gruber. “If you think Google isn’t building a proprietary Chrome platform, your head is in the sand.”

There’s some hope, though. “Helping to establish developer habits that support the growth of the open web remains a focus for the Chrome team and Google overall in 2018,” says Google’s Ben Galbraith. It’s a focus that both the Chrome and Google’s web teams will need to closely align on to avoid Chrome-only sites.

Microsoft might have celebrated the death of Internet Explorer 6, but if Google isn’t careful then it might just resurrect an ugly era of the internet where “works best with Chrome” is a modern nightmare.

Update, 2:20PM ET: Clarified additional detail on Google’s services support for Firefox and Edge browsers. Updated again at 12:05 ET on Jan 5 to include Groupon’s treacly walkback of Chrome-only support in a tweet.