Why it matters: It’s been more than three years since it launched, but Windows 10 has passed the milestone Microsoft has been waiting for: the platform is now the most popular desktop operating system, having finally grabbed a larger market share than Windows 7.

Back when Windows 10 arrived in 2015, Microsoft famously said it planned to have the OS installed on one billion devices by 2018. One year later, it admitted that prediction was overly optimistic—partly because of the demise of the Windows Phone.

But new Windows 10 installs have continued growing at a strong and steady pace and reached almost 700 million devices back in May. Yet despite the free upgrade offers and Microsoft’s pushy, occasionally malware-like tactics to get people to move to its newest OS, Windows 7 retained the larger market share, mostly due to its popularity among enterprise users.

According to Net Market Share, however, all that changed in December when Windows 10’s worldwide market share jumped 1.08 percent to 39.22 percent, while Windows 7’s declined by 1.99 percent to 36.90 percent. Mac OS X 10.14 sits in third place with 4.73 percent, and Windows XP is fourth with 4.54 percent.

Interestingly, Windows' market share as a whole declined slightly between November and December, falling from 87.03 percent to 86.2 percent. Mac OS' share, meanwhile, went up from 9.71 percent to 10.65 percent.

With just over one year left before Microsoft ends extended support for Windows 7, expect to see Windows 10 continue to increase its market share.