brackets live preview for mozilla firefox developer edition

Currently using Brackets to Live Preview on Mozilla Firefox (not on the Developer Edition). I've tried Live Preview on Waterfox but I can't seem to remember if it worked or not.

Anyways, try this:

Open Brackets then on the upper part of the window, click the "Debug" button. On its drop down menu click the "Open Preference File".

On my version of Brackets (which is the latest) it will open up two .json files: 1)defaultPreferences.json and 2) brackets.json. Just focus on "brackets.json". (If ever that the first .json file never pops-up, it's fine).

Then proceed to add this line inside the bracket:

"livedev.multibrowser": true,

I suggest putting this on top of the default lines. So for example, it would look like this:

 {
    "livedev.multibrowser": true,
    "fonts.fontSize": "12px",
    "fonts.fontFamily": "'SourceCodePro-Medium', ＭＳ ゴシック, 'MS Gothic', monospace",
    "themes.theme": "dark-theme"
 }

Hope this helps. If it doesn't, I suggest bringing it over to the devs.

Use File->Enable Experimental Live Preview. See documentation here https://github.com/adobe/brackets/issues/12260