The browser-maker’s wannabe rival to Android and iOS saw a few years of activity, finding its way into low-cost handsets from manufacturers like ZTE and Alcatel. It was enthusiastically backed by mobile carriers such as Telefonica, who desperately wanted a mobile platform that would give more power to them, rather than Google (GOOG) or Apple (APPL).

Many app developers really liked the idea too, because Firefox OS is based on open web technologies and its apps can also run on Android and desktop platforms. However, in December Mozilla said it was “pivoting” Firefox OS from mobile to other connected devices (it powers Panasonic TV sets, for example) and would stop rolling out new handsets with carrier partners.

On Thursday, Mozilla unveiled the full death schedule for Firefox OS as a mobile platform.

Get Data Sheet, Fortune’s technology newsletter.

The next version, 2.6, due to come out in May, will be the last. The Firefox OS mobile marketplace will start to shut down from March 29, initially closing to new app submissions for Android, desktop and tablet, then to Firefox OS-specific apps sometime in 2017.

“Obviously, these decisions are substantial,” wrote John Bernard and George Roter, Mozilla’s chief liaisons with its core contributor community.

“The main reason they are being made is to ensure we are focusing our energies and resources on bringing the power of the web to [the Internet of things]. And let’s remember why we’re doing this: We’re entering this exciting, fragmented space to ensure users have choice through interoperable, open solutions, and for us to act as their advocates for data privacy and security.”

For more on Android, watch:

Bernard and Roter wrote that the entrenched status of Android and iOS (though they didn’t name them) meant “we were playing catch-up, and the conditions were not there for Mozilla to win on commercial smartphones.” Still, the project showed the web was flexible enough to underpin a range of product types.

Technically, geeks can still carry on developing the OS if they like, but Mozilla won’t put in any staff time past May.

In the comments, Firefox OS contributors expressed a fair amount of disappointment. “Please don’t throw [in] the towel on phones, it’s been slow and hard but to me it seemed that finally the OS was coming along nicely,” wrote “Jorrete,” adding: “It’s not realistic to expect that the community will keep Firefox OS for phone without the Mozilla engineers as it is today.”

For more on iOS, read: Apple iOS 9 Update Fixes User-Impersonation Bug

Meanwhile, Andre Alves Garzia pointed out that Mozilla was surrendering the opportunity to let tinkerers develop new control mechanisms for the smart home, independently of big players like Google and Apple: “The Connected Home will be mainly interacted with from mobile devices…You just lost your hacker friendly platform.”

That may be, but with Android holding around 85% of the smartphone OS market, iOS holding around 13%, and Firefox OS being lumped in the 0.3% “others” category behind Windows and the near-dead BlackBerry OS, the project simply didn’t take off.

It seems buyers of low-cost phones were more interested in buying into the big mobile ecosystems than they were in hackability and open web standards. There was only so long Mozilla could keep putting resources into a proven failure.