opacity in Firefox 3.5

This is a very short post, but it’s worth putting up because it shows how browser features go from a vendor-specific implementation to a fully supported standard.

In Firefox 3.5 we no longer support the Mozilla-specific CSS property -moz-opacity. Developers wanting to set the opacity of an element should use the standard <a href="https://developer.mozilla.org/en/CSS/opacity">opacity</a> property instead.

We introduced the opacity property way back in Firefox 0.9 and -moz-opacity was deprecated. And with Firefox 3.5 we’ve finally removed it.

A long road for a simple property, but it’s worth mentioning so people understand the time scale for these kinds of features and how they relate to standards.


  1. […] 原文地址:opacity in Firefox 3.5 系列地址:颠覆网络35天 […]

    June 23rd, 2009 at 23:10

  2. Gerv

    Anyone else seeing a strange rendering glitch on this blog where the “content” div, which has a white background, has zero height? It makes things very hard to read (grey on grey)…

    Mozilla/5.0 (X11; U; Linux i686; en-GB; rv:1.9.1) Gecko/20090616 Firefox/3.5


    June 24th, 2009 at 02:29

  3. Christopher Blizzard

    @Gerv – working fine here?

    June 24th, 2009 at 08:14

  4. Keen Dreams

    I wish CSS had a way to specify that a container should be exempt from the opacity of its parent, or that a container’s opacity shouldn’t apply to its children…

    June 24th, 2009 at 18:30

  5. Gerv

    Chris: seems to have fixed itself.


    June 25th, 2009 at 01:22

  6. Wladimir Palant

    Keen, that’s how -moz-opacity worked before Firefox 0.9 when the implementation was changed to conform to the standard (which is more logical but also less flexible). You can get a similar effect by using rgba() colors however.

    June 25th, 2009 at 04:08

  7. Theodora Vorbix

    border-radius, box-shadow and text-shadow should be next in line,

    June 25th, 2009 at 20:48

  8. Tiger1vic

    Thanks for this info! After upgrading to FF 3.5, I was unable to view floor plans in my Cisco WCS (wireless control system). Turns out this is how they overlay the WCS heat maps on top of the floor plans. After my browser upgrade, all I saw was the heat map with no location info. A few simple substitutions in the wcs.css file and it now works properly again!

    July 6th, 2009 at 13:54

  9. adam

    I would love to know what that WCS fix is Tiger Ivic, I’m having the same problem and am not much of a web designer :(

    July 7th, 2009 at 09:01

  10. Ed

    I also would love to know the WCS replacements you made.


    July 10th, 2009 at 06:38

  11. […] artykułów z bloga Mozilla Hacks, przedstawiam dzisiaj tłumaczenie (króciutkiego) artykułu Opacity in Firefox 3.5, autorstwa Chrisa […]

    July 27th, 2009 at 13:26

  12. […] 原文地址:opacity in Firefox 3.5 系列地址:颠覆网络35天 […]

    August 9th, 2009 at 20:55

  13. thxraph

    @adam & Ed: as stated on this post, beeing it’s main purpose, he replacce the old “-moz-opacity” -deprecated & now removed- to “opacity” in the CSS file.

    September 17th, 2009 at 04:19

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