On my older HTC Gingerbread device, Firefox uses the system default download folder, which in my case is on the SD card already.

To change the download folder for Firefox only:

(1) Open a new tab to about:config (type about:config in the Awesomebar and tap the go arrow or tap Enter)

(2) In the search box, type down and tap Enter

(3) Scroll down to browser.download.folderList and tap Modify, then change the value from 1 to 2 (from default always to last used folder). The change should appear after a few seconds.

(3) Scroll back up and tap the "Add a New Setting" button

(A) String is the correct type, so OK that

(B) The name of the preference should be browser.download.dir (this stores the last used directory)

(C) The value should be /sdcard/ followed by the folder name you want to use, for example, /sdcard/FxDown

If you switch back to your other tab and download something, it should go to the new folder.

Any luck?

Hi rob419, another user had the same question. Did you find a solution? If so, do you want to share it here: https://support.mozilla.org/en-US/questions/980785

Your answer was really helpful.. What are other values of download.folderlist eg. 3,4 etc.?

Hi Heminshah90, apparently "0" means desktop on Firefox for regular PCs.

I don't think anything other than 0, 1, or 2 does anything useful.