Targeting only Firefox with CSS

661
votes

Using conditional comments it is easy to target Internet Explorer with browser-specific CSS rules:

<!--[if IE 6]>
...include IE6-specific stylesheet here...
<![endif]-->

Sometimes it is the Gecko engine (Firefox) that misbehaves. What would be best way to target only Firefox with your CSS rules and not a single other browser? That is, not only should Internet Explorer ignore the Firefox-only rules, but also WebKit and Opera should.

Note: I'm looking for a 'clean' solution. Using a JavaScript browser sniffer to add a 'firefox' class to my HTML does not qualify as clean in my opinion. I would rather like to see something that depends on browser capabilities, much like conditional comments are only 'special' to IE…

12
cssfirefoxcss-hack
Might want to look at some similar questions and thier related answers... stackoverflow.com/questions/738831/… – AnonJr
is there any way to target firefox on a windows machine vs a mac? – Kegan Quimby
<!--[if Gecko ]> ...include... <![endif]--> – defines

12 Answers

1338
votes

OK, I've found it. This is probably the cleanest and easiest solution out there and does not rely on JavaScript being turned on.

@-moz-document url-prefix() {
  h1 {
    color: red;
  }
}
<h1>This should be red in FF</h1>

It's based on yet another Mozilla specific CSS extension. There's a whole list for these CSS extensions right here: Mozilla CSS Extensions.

135
votes

Updated(from @Antoine comment)

You can use @supports

@supports (-moz-appearance:none) {
    h1 { color:red; } 
}
<h1>This should be red in FF</h1>

More on @supports here

83
votes

Here is how to tackle three different browsers: IE, FF and Chrome

<style type='text/css'>
/*This will work for chrome */
#categoryBackNextButtons
{
    width:490px;
}
/*This will work for firefox*/
@-moz-document url-prefix() {
    #categoryBackNextButtons{
        width:486px;
    }
}
</style>
<!--[if IE]>
<style type='text/css'>
/*This will work for IE*/
#categoryBackNextButtons
{
    width:486px;
}
</style>
<![endif]-->
16
votes

Here is some browser hacks for targeting only the Firefox browser,

Using selector hacks.

_:-moz-tree-row(hover), .selector {}

JavaScript Hacks

var isFF = !!window.sidebar;

var isFF = 'MozAppearance' in document.documentElement.style;

var isFF = !!navigator.userAgent.match(/firefox/i);

Media Query Hacks

This is gonna work on, Firefox 3.6 and Later

@media screen and (-moz-images-in-menus:0) {}

If you need more information,Please visit browserhacks

13
votes

First of all, a disclaimer. I don't really advocate for the solution I present below. The only browser specific CSS I write is for IE (especially IE6), although I wish it wasn't the case.

Now, the solution. You asked it to be elegant so I don't know how elegant is it but it's sure going to target Gecko platforms only.

The trick is only working when JavaScript is enabled and makes use of Mozilla bindings (XBL), which are heavily used internally in Firefox and all other Gecko-based products. For a comparison, this is like the behavior CSS property in IE, but much more powerful.

Three files are involved in my solution:

  1. ff.html: the file to style
  2. ff.xml: the file containg the Gecko bindings
  3. ff.css: Firefox specific styling

ff.html

<!DOCTYPE html>

<html>
<head>
<style type="text/css">
body {
 -moz-binding: url(ff.xml#load-mozilla-css);
}
</style>
</head>
<body>

<h1>This should be red in FF</h1>

</body>
</html>

ff.xml

<?xml version="1.0"?>

<bindings xmlns="http://www.mozilla.org/xbl">
    <binding id="load-mozilla-css">
        <implementation>
            <constructor>
            <![CDATA[
                var link = document.createElement("link");
                    link.setAttribute("rel", "stylesheet");
                    link.setAttribute("type", "text/css");
                    link.setAttribute("href", "ff.css");

                document.getElementsByTagName("head")[0]
                        .appendChild(link);
            ]]>
            </constructor>
        </implementation>
    </binding>
</bindings>

ff.css

h1 {
 color: red;
}

Update: The above solution is not that good. It would be better if instead of appending a new LINK element it will add that "firefox" class on the BODY element. And it's possible, just by replacing the above JS with the following:

this.className += " firefox";

The solution is inspired by Dean Edwards' moz-behaviors.

11
votes

Using -engine specific rules ensures effective browser targeting.

<style type="text/css">

    //Other browsers
    color : black;


    //Webkit (Chrome, Safari)
    @media screen and (-webkit-min-device-pixel-ratio:0) { 
        color:green;
    }

    //Firefox
    @media screen and (-moz-images-in-menus:0) {
        color:orange;
    }
</style>

//Internet Explorer
<!--[if IE]>
     <style type='text/css'>
        color:blue;
    </style>
<![endif]-->
8
votes

A variation on your idea is to have a server-side USER-AGENT detector that will figure out what style sheet to attach to the page. This way you can have a firefox.css, ie.css, opera.css, etc.

You can accomplish a similar thing in Javascript itself, although you may not regard it as clean.

I have done a similar thing by having a default.css which includes all common styles and then specific style sheets are added to override, or enhance the defaults.

7
votes

Now that Firefox Quantum 57 is out with substantial — and potentially breaking — improvements to Gecko collectively known as Stylo or Quantum CSS, you may find yourself in a situation where you have to distinguish between legacy versions of Firefox and Firefox Quantum.

From my answer here:

You can use @supports with a calc(0s) expression in conjunction with @-moz-document to test for Stylo — Gecko does not support time values in calc() expressions but Stylo does:

@-moz-document url-prefix() {
  @supports (animation: calc(0s)) {
    /* Stylo */
  }
}

Here's a proof-of-concept:

body::before {
  content: 'Not Fx';
}

@-moz-document url-prefix() {
  body::before {
    content: 'Fx legacy';
  }

  @supports (animation: calc(0s)) {
    body::before {
      content: 'Fx Quantum';
    }
  }
}

Targeting legacy versions of Firefox is a little tricky — if you're only interested in versions that support @supports, which is Fx 22 and up, @supports not (animation: calc(0s)) is all you need:

@-moz-document url-prefix() {
  @supports not (animation: calc(0s)) {
    /* Gecko */
  }
}

... but if you need to support even older versions, you'll need to make use of the cascade, as demonstrated in the proof-of-concept above.

3
votes

The only way to do this is via various CSS hacks, which will make your page much more likely to fail on the next browser updates. If anything, it will be LESS safe than using a js-browser sniffer.

1
votes

CSS support has binding to javascript, as a side note.

if (CSS.supports("( -moz-user-select:unset )")) {
    console.log("FIREFOX!!!")
}

https://developer.mozilla.org/en-US/docs/Web/CSS/Mozilla_Extensions

0
votes

The following code tends to throw Style lint warnings:

@-moz-document url-prefix() {
    h1 {
        color: red;
    }
}

Instead using 

@-moz-document url-prefix('') {
    h1 {
        color: red;
    }
}

Helped me out! Got the solution for style lint warning from here

0
votes

with -moz prefix

div:-moz-read-only {
  background: green;
}

textarea:-moz-read-write {
  background: green;
}

:-moz-any(div#foo) div.bar {
  background: green;
}

li:-moz-first-node, li:-moz-last-node {
  background: green;
}