Responsive Design Mode is only available for remote browser tabs, such as those used for web content in multi-process Firefox.
Na'onel rub'anikil wachib'enïk xa xe okel pa taq ruwi' näj okik'amaya'l, achi'el ri ye'okisäx richin rupam ajk'amaya'l pa jalajöj taq rub'eyal Firefox