Mozilla clarifies what the removal of full themes actually means

Martin Brinkmann
Nov 10, 2015

Mozilla announced last Friday that it plans to remove heavyweight theme support from the Firefox web browser in a bug listing on the organization's official bug tracking website.

Back then, Benjamin Smedberg, one of Mozilla's senior Engineers, mentioned that Mozilla decided to "stop support for "heavyweight" themes which can do arbitrary styling and replace chrome packages" and that the organization may simply remove support or extend lightweight themes with additional features depending on how the discussion progresses.

The negative reaction to the announcement on Bugzilla and also other sites who mentioned it caused Mozilla's Kris Maglione to emphasize that the bug listing was not "just about removing support for heavyweight themes" but also for for deciding what the future of theme support in Firefox would look like.

I would just like to point out that this bug is not just about removing support for heavyweight themes. It's also about coming up with a plan what kind of theming support we want to add to replace them.


Another Mozilla employee, Kev Needham confirmed Maglione's assessment of the situation.

The point of this bug is to start to lay the groundwork for what themes support will be in the future, with the goal of making them simpler to create and maintain. This bug isn't meant to say "we're killing Complete Themes in Firefox", it's the starting point for planning what happens with them moving forward, and scoping what we can support and how.

firefox full theme
A complete theme for Firefox

Maglione highlighted the reason behind the decision in the same post on Bugzilla stating that current heavyweight themes "are not sustainable".

The basic fact of the matter is this: heavyweight themes, in their current form, are not sustainable. They require a complete reimplementation of the Firefox front-end CSS for every theme. They require significant, painstaking updates for every release (which happen *much* more often now than they did when the feature was designed). They require a massive amount of energy by both Firefox developers and third-party theme developers to keep alive. Most themes fall by the wayside after a couple of years (and that's being optimistic).

Mozilla basically wants to change what complete themes can do in the same way that it plans to change what add-ons can do in Firefox. The organization announced back in August 2015 that it would deprecate XPCOM and XUL based add-ons in favor of a new Web Extensions API.

Back then it asked for user and especially add-on developer input as to what the API should offer, and it is the same this time for themes.

Several add-on developers announced afterwards that they would stop development of their add-ons for Firefox, and it is likely that the same is going to happen in regards to the few theme developers who are still working on full themes for the browser.

While it is too early to tell how theme support will look like in Firefox once Mozilla is done with the changes, it is likely that it will be still superior to Chrome theming but less powerful than before.

Mozilla clarifies what the removal of full themes actually means
Article Name
Mozilla clarifies what the removal of full themes actually means
Mozilla has clarified what it meant when it stated that complete theme support would be removed from Firefox in the future.

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  1. anohana said on November 10, 2015 at 1:16 pm

    It would be much better if they communicate like this. However, it seems pathetic to me. They just want to save the sinking ship.

  2. John said on November 10, 2015 at 1:27 pm

    Roughly translates to them saying:

    Mayday! Mayday! This ships going down
    And as your captain I’m ready to drown…

  3. Tom Hawack said on November 10, 2015 at 2:35 pm

    I agree when anohana emphasizes on communication even if I don’t perceive anything pathetic about it.
    Condemning lack of communication/explanations then criticizing when it occurs seems to me close to deep hatred! Live and let live, not die :)

  4. Ben said on November 10, 2015 at 2:55 pm

    So I won’t be able to use custom css to style FF as I want?
    If yes, this is an even worse idea than removing basically most addons with the API stuff.

  5. Dan82 said on November 10, 2015 at 3:06 pm

    The unfortunate truth is, that Mozilla find themselves in rough waters and it is no fault but their own because they have willfully steered the ship there themselves.
    I first used the browser when it wasn’t even called Firefox yet, but I really began using it regularly once extensions were implemented and took off in late 2004. Although it hasn’t always been my primary browser (over long periods of time Opera was just better), the wide customizability and the many helpful extensions never let me leave Firefox entirely.
    To be fair, I understand the need for a complete redesign of the way themes and extensions are connected to the core of the browser. After more than a decade it stands to reason that enough development has been done to find a better (faster, more efficient) way to do many things. The problem I see with this revolution however, is not in the change itself but in the way Mozilla has started to behave in the past few years. In their desire to catch up to the new leader on the browser market, they have bulldozed their way through a decade of Firefox tradition and left behind a wasteland of former users. There is a reason why people are skeptic about the upcoming extensions API, because it will most likely cause a number of interesting extensions to be impossible to implement under the new system even if those developers were willing to spend their time on a complete redesign.
    If Mozilla keeps up with the current trend, namely removing features that previously allowed users to customize their browsing experience, then the Firefox will reach its expiration date in mid 2017 for me and many other people. What reason is there to remain faithful to Firefox anymore, when its feature-set has been reduced to the lowest common denominator called Chrome? None, or I would’ve started using Chrome from 2008-10 on.

    1. LimboSlam said on November 11, 2015 at 3:41 am

      Yep! I’ve spoken with a few and they won’t do it, some even quit. Sad…….. :(

  6. Earl said on November 10, 2015 at 3:14 pm

    What is “not sustainable” is Mozilla’s roadmap for the future of Firefox. They’re heading straight to a dead end.

  7. Dan82 said on November 10, 2015 at 3:15 pm

    @ Martin : unrelated to this specific blog entry, I’d just like to ask if you changed anything with the comment system recently or if the problem is on my end.

    I was trying to edit the post I’ve made earlier to improve on my grammar. While I got the edit form just fine, when saving the changes I received an error message that I couldn’t edit this post anymore. That’s strange, because I only took some 30 seconds to change a few passages of text and I certainly didn’t use up all the ~6 minutes of time I had left on the counter when I started the editing process.

    1. Martin Brinkmann said on November 10, 2015 at 3:28 pm

      Dan, no I have not made any changes. The plugin did upgrade recently though. Can you keep an eye on it and let me know if it happens again?

      1. LimboSlam said on November 11, 2015 at 3:36 am

        Yes I’ve been getting this too.

  8. SOjiro84 said on November 10, 2015 at 3:44 pm

    Another nail in the coffin called Firefox.

    I bet that the end result of their themes is probably the same as it is in Google Chrome. Same lame colours that can be adjusted with a shitty picture as a background in the browser.

    First they are limiting addon possibilities and now they are destroying themes.

    1. Anonymous said on November 11, 2015 at 10:26 pm

      Exactly what I was thinking. I have trust issues with developer giving these kind of promises for the future and such. I’ve just seen these kind of empty promises too much now.

    2. Anonymous said on November 12, 2015 at 3:32 pm

      Chrome’s theming is at least miles better than Firefox’s lightweight theming.

  9. Joker said on November 10, 2015 at 6:57 pm


    “They require a massive amount of energy by both Firefox developers and third-party theme developers to keep alive.”

    How much energy do useless stuff like Hello, Pocket and ads/tracking on about:newtab require?

    1. LimboSlam said on November 11, 2015 at 3:38 am

      I know right!

    2. Lestat said on November 11, 2015 at 2:39 pm

      That is what simple users want, use or need. And as this is Mozilla’s new target user base, they implement those features instead of customization choices.

      It is always sad when a software developer decides that a simple, less demanding target group is suddenly more important than the one which wants features, options and want to have almost total control in how the browser looks and works.

      And it is even more worse when a software developer just betrays it’s very core user group which supported it from the very beginning!

      But you know, the king is dead, long live the new king :)

      All replacement browsers with more honest, faithful developers which see no reason to kill of features to be able to compete with the lowest common denominator called Google Chrome!

  10. Elafym said on November 11, 2015 at 3:08 pm

    Mozilla devs: “Hey guys! We’ve decided for whatever reason to break yet another feature of Firefox you’ve been enjoying for years. Any idea on how to fix it now?”

    Everyone else: “Just don’t break it to begin with!”

  11. Wicked said on November 15, 2015 at 9:46 am

    Well crap! I have usd Firefox since about 1998, I do believe. Between borking my favorite add-ons that I have used for years, this theme mutilation stuff and a few other annoyances that have cropped up over the last four years, I am ready to use another browser. But what? I hate Chrome. It uses too many resources on my system. I hate IE/Edge…just because I have hated it for so long. I did not care for Cyberfox, and Pale Moon worried me because I do not know if it is truly secure enough in the current web environment. I enjoyed using it, but I worry that my password safes could be compromised if I use them in the browser.Still, I guess Pale Moon will be the one I use.

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