* Some Firefox Desktop versions distributed by third-parties, especially Linux distros use MLS by default. Currently this includes Firefox for Fedora and Firefox on ArchLinux.
* [https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=726230 Iceweasel might use MLS in the future].
===Firefox OS===
* [https://github.com/clochix/FxStumbler FxStumbler] is a prototype of a stumbling app for Firefox OS.
* OS level support for stumbling is available since Firefox OS 2.5.
===Android===