It's too small to read.

Bug report is https://bugzilla.mozilla.org/show_bug.cgi?id=143119

Notice: it's not about Firebug.

3 Answers 3


In Firefox 27, Codemirror is now deployed as the default code editor:


Codemirror is a popular HTML5-based code editor component used on web sites. It is customizable and theme-able. The Firefox Devtools now use CodeMirror in various places: Style editor, Debugger, Inspector (Edit as HTML) and Scratchpad.

From the Option panel, the user can select which theme to use (dark or light).

Source: Firefox Developer Tools: Episode 27 – Edit as HTML, Codemirror & more

This works for me in ~/.mozilla/firefox/profile-name/chrome/userChrome.css.

@namespace url(http://www.w3.org/1999/xhtml);
@-moz-document regexp("chrome://browser/content/devtools/.*"){
* { font-size: 20px !important }

enter image description here


The easiest workaround for me was changing DPI value in KDE font settings. Now all other fonts are too big but at least I can read the debugger.

  • 2
    I think your correct edit was rejected because I was editing to add extra info. Sorry about that. I made the edit you suggested.
    – DK Bose
    Feb 26, 2014 at 11:52

You can also create userChrome.css in:

/usr/lib/firefox-dev/browser/chrome/ (32 bit)

/usr/lib64/firefox-dev/browser/chrome/ (64 bit)

It worked for me when I created userChrome.css in /usr/lib64/firefox-dev/browser/chrome/ folder. This should also make your changes global.

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