How could I upgrade my Firefox for Android directly?

You can download the apk and install Firefox manually however the Release and beta versions do not update in Firefox on Android this way as you would have to manually install each new release. http://download.cdn.mozilla.net/pub/mozilla.org/mobile/releases/latest/android/en-US/ However if you phone or tablet has a older ARMv6 cpu or a Intel Atom instead of the most common ARMv7 cpu then see http://download.cdn.mozilla.net/pub/mozilla.org/mobile/releases/26.0.1/ The other option is to install Aurora channel build as it will then do software updates each day. It is where 28.0a2 is currently being developed on until move/merge to Beta channel in early February . http://download.cdn.mozilla.net/pub/mozilla.org/mobile/nightly/