Although users can temporarily switch back to the old interface on Facebook's site, the button warns that "the classic Facebook will no longer be available starting in September."
The new interface was announced at Facebook's developer conference last year and initially rolled out on the service's iOS and Android apps.
In March, it got a widespread release on desktop, as an opt-in feature, leaving people free to continue using the old design if they want to. However, in September, the old design will disappear.
The Verge reported that the new interface is a big change from what Facebook has used for most of its existence. The new interface is expected to be a lot cleaner and should include a lot more white space, and there's also a dark mode.
Functionally, it also places a bigger focus on the service's Groups features, as well as prominently displaying links to Facebook's Watch, Marketplace, and Gaming sections in its top navigation bar.