Firefox: new default theme, theme API makes an appearance

Martin Brinkmann
Jan 16, 2017
Updated • May 23, 2018

2017 will be quite the interesting year for the Firefox web browser. Mozilla plans to make the switch to WebExtensions in that year, launch a new themes API that is based on that, and will introduce a new default Firefox theme on top of all that.

The first changes have been pushed to the Nightly version of the Firefox web browser already. The most visible change is the addition of two new themes that Firefox will ship with from that version on.

What this means is that Firefox users can choose one of the three themes to run Firefox with, all without having to head over to the themes repository to download themes first.

Firefox: new default compact themes

Users of Firefox's Developer Edition may know the themes already: Compact Dark and Compact Light are more or less copies of the Developer Themes.

The core difference is that you may enable the themes using the Add-on Manager, and don't have to open the Developer Tools to switch between themes. Their main advantage over the default theme is that they save you a couple of extra pixels vertically when enabled.

The new themes are already available for selection in Firefox Nightly. They will be made available in other Firefox versions in the coming months.

To enable them, load about:addons in the browser's address bar, and switch to appearance in the menu. There you find the two new themes listed next to the default theme, and any other theme you may have installed in Firefox manually.

Simply click on the enable link to activate the selected theme. A restart is not required.

Another option that you have to enable the themes is to open the browser's customize mode. Click on Menu > Customize.

Select Themes to display the list of themes. Firefox displayed the default theme there, and five recommended themes. The new themes listing there displays the two compact themes for selection, and only two recommended themes instead of five.

Theme WebExtensions API has landed

webextensions themes

Mozilla is working on WebExtensions support currently. Some APIs are already available, and many are still being worked on.

One API that was a no-show up until now was the new theme API that will provide theme developers with capabilities to create themes for the Firefox web browser.

This is important, as Mozilla wants to turn off all other add-on and theme related creation options, and focus solely on WebExtensions starting in late 2017.

All themes and add-ons for Firefox that are not created using WebExtensions won't be compatible with Firefox anymore at that point. While it is possible that Mozilla will extend the deadline to give developers more time to make the switch, nothing has been said in this regard up to now. Specifics are not known yet and it remains to be seen how this will end up.

The new themes API will sit somewhere between today's lightweight themes and full themes. It will be more powerful than lightweight themes, but not as powerful as full themes.

The new theme WebExtensions API has landed in Firefox Nightly. It is locked behind a configuration switch right now though:

  1. Type about:config in the Firefox address bar.
  2. Confirm that you will be careful if the warning prompt appears.
  3. Search for extensions.webextensions.themes.enabled.
  4. Double-click the preference.

This sets the preference to true, and enables support for the WebExtensions themes API in Firefox. You can follow development of the themes API -- it is far from complete -- here.

New Firefox Default Theme

Mozilla plans to refresh the current default theme of the Firefox web browser in 2017. The project is called photon, and it is part of Quantum, but that is the extent of what we know about the plans right now.

It could be a simple visual refresh, or something of epic proportions like Australis.

Closing Words

Much of what is theme-related and coming in 2017 is unknown territory at this point in time. We don't know anything about the default theme refresh, nor how powerful the themes API will be once version 1.0 is made available. (thanks Sören Hentzschel)

Now You: What are your expectations for the new default theme, and themes API?

Firefox: new default theme, theme API makes an appearance
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Firefox: new default theme, theme API makes an appearance
Mozilla plans to launch a new theming API that is based on WebExtensions, and will introduce a new default Firefox theme in the year 2017.
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  1. Mom_4Angels said on November 24, 2017 at 11:22 pm

    I have used FF since inception…with these changes: taking MY customization abilities through Themes (full) and extensions such as script block & colorful tabs…I will leave FF now because it looks like IE! YUK…sorry, I know you are trying to update features but you have taken those important to me away…wish I hadn’t had my Windows system to automatically update as I would NOT have chosen Quantum over my version prior to 57 had I known my themes would be gone with no option to enable them again! Well, at least my Linux system is several versions behind & shouldn’t auto update and take away my themes…so sad right now!

  2. Burg3rLov3r said on January 17, 2017 at 9:08 am

    Somehow I get the feeling that the new theme will be very flat and ugly… as is the trend these days.

  3. hahaha said on January 17, 2017 at 3:54 am

    I am just starting to switch from Firefox to chrome-based browsers recently… We no longer need Firefox when it becomes another Chrome.

    1. Dr. Who said on January 17, 2017 at 1:42 pm

      Not to mention “Firefox is Chrome” is an old meme based on cherry picking and other cognitive biases I would be ashamed to be caught into. (Though nobody is immune)

    2. www said on January 17, 2017 at 12:16 pm

      Don’t you have anything better to do besides troll? I doubt you were even a FF user to begin with.

      Do you think your trolling will get us all to switch to chrome? hahaha

      1. www said on January 18, 2017 at 12:54 pm

        Ah, the troll has spoken. Glad I got a rise out of you. But I shouldn’t be surprised by it coming from an immature assh0le like you.

        Not to mention you’re a lair to boot. hahahah :D

      2. hahahah said on January 17, 2017 at 4:33 pm

        Trolling? That’s you! And you are bullshxtting !! FXXK YOU!!

        I have been using Firefox since 3.0 !!

        Just keep your fxxking asshole on the new coming FireChrome !!

    3. Jed said on January 17, 2017 at 10:53 am

      Currently I’m stuck inbetween browsers. I would like to switch to Chrome, but unfortunately Chrome doesn’t have NoScript, it has no RSS support, and if they decide to change the interface we’re stuck with it as Google aren’t providing any customisation options.

  4. greg said on January 17, 2017 at 1:11 am

    So are the compact themes similar to the old Small Icons option? The current default theme is WAY to fat and tall for my tastes.

  5. foxuser said on January 16, 2017 at 9:55 pm

    What is compact about the compact themes?

    I’m asking because in the screenshots there are these items at the top:

    – row of menu buttons (file, edit, …)
    – empty space
    – the tab row with plenty of padded space on top and bottom of each tab
    – a small padded line
    – buttons and url bar
    – a small padded line
    … and finally the webpage is show

    Waste of vertical space!

  6. Tom Hawack said on January 16, 2017 at 7:51 pm

    Whatever the theme I’m practically sure I’ll have to tailor it to my preferences, both aesthetic and functional. So I care much more about having the possibility to stylize Firefox with css then to have whatever theme at disposal. That’s for me but I do understand a newcomer will be delighted to switch from light to dark with one click. I do hope the ‘Classic Theme Restorer’ Firefox add-on will remain active once the WebExtensions will have completely taken the relay because if I have to endure Mozilla’s talent for graphics it’ll be a tough challenge. If we focus on a browser’s graphic design only (I know, it’s not the main thing in a browser) then i’ll acclaim the Opera browser I had several years ago : gorgeous. Guess it’s still as elegant nowadays.

  7. Dan82 said on January 16, 2017 at 2:49 pm

    Quote: “Now You: What are your expectations for the new default theme, and themes API?”

    They are very very low. I’ve recently spied a WebExtensions API request by Aris (the guy who developed and maintains Classic Theme Restorer) being denied on the same day it was made without any kind of discussion or input from other interested people. It underscores that Firefox is being developed into the direction I have always feared would happen and the extensions API merely follows that general trend. In case anyone is interested in reading, here’s the original link:

    My Firefox would not be productive without the must-have extensions TabMixPlus and Classic Theme Restorer and their contributions to getting the most out of the browser interface. Anything less I couldn’t imagine living with while still using the same browser and it’s the one reason why I remain underwhelmed about the future outlook.

    Of course, WebExtensions will ship with theming support, but what we’ll receive and what we’ve had will be very different things. You only need to look at the link I provided, what kind of things Aris wants his suggested API to support and the universal dismissal of the idea. Because of this I’ve started thinking of future Firefox theme support like the one in Chrome – if I keep to that, then anything more will be a positive surprise. I believe in regards to Firefox we could all do with a few of those for a change.

    1. Homer said on January 16, 2017 at 10:04 pm

      To be fair that bug from Aris was essentially a polite troll: He basically asks for WebExtensions to not exist. He says he wants everything XUL does, while this not being true is one of the five or so design points that make WebExtensions.

      Since WebExtensions are going to exist, of course his bug is a WONTFIX.

      That doesn’t mean we must not push Mozilla for a strong enough theming API. Watch them out this year.

  8. Homer said on January 16, 2017 at 2:07 pm


    Please be mindful of fingerprinting issues related to window/screen/viewport sizes and position. Customisability should not be hampered by such concerns but it’s important that Firefox can provide uniform fingerprint in spite of fragmentation caused by user customisation of the viewport.

  9. DaveyK said on January 16, 2017 at 12:56 pm

    I’m hoping for a bigger refresh. Australis (by and large) was a disaster. Not necessarily for the way it looked (although I was not a fan), but because it dispensed with a lot of cusomisability. I’d therefore like to see a technical re-working as well as an overhaul of the visuals. Specifically, add back the ability to split the back/forwards buttons, and to move the stop/refresh buttons around for example. Some extra bits such as the availability of the status bar and tabs-on-bottom would be good too, even if not enabled by default.

    In order to succeed, Firefox needs some USPs. Previously, customisability and strength of their add-on eco system were their two biggest strengths against Chrome and IE. Mozilla need to capitalise on this by realising the Australis changes that drove away so many users and fixing them to try and tempt some of these users back.

  10. MdN said on January 16, 2017 at 12:48 pm

    Is there a way, a .css script perhaps, to change the blue highlight color of the developer edition theme to some other color?

  11. Anonymous said on January 16, 2017 at 12:18 pm

    Recommended theme:
    “A Web Browser Renaissance” by mart3ll: “We are seeing constant advancement from the static browsing Middle Ages of old and the ushering in of a new Modern Era of openness, speed and security.”
    From the same author of this theme, right next another “New Modern Era of openness”: ACK Buddha theme, ACK Shiva theme, etc.

    Proselytizing has no Age. And what later, ads? No thanks Mozilla.

    1. Homer said on January 16, 2017 at 2:01 pm

      A town that provides a mosque, a church and a synagogue and treats them all the same is definitely not doing proselytism. You might want to check a dictionary. You can find add-ons of all kinds for your browser and it’s your choice to install them or not.

      1. Anonymous said on January 17, 2017 at 7:45 am

        @Homer: I should have written “Recommended theme” by Mozilla (firefox-add-themes – screenshot 4) sorry.
        Remember this place for Mozilla’s recommendations is also the place for data collection, this is is really worrying IMO, it does not augur well…

      2. Homer said on January 16, 2017 at 9:47 pm

        Ah! You didn’t mean to talk about religious proselytism. Ok then, well yeah when you recommend something you are effectively filtering content so yeah, it is “proselytism”, as opposed to purely objective search relevance like search engines of old. (Google nowadays does tweak its search results based on what it thinks is best for you, and Facebook even more so.)

        Whether we like the suggestion or not doesn’t change the fact that there is non-objective shit going on.

      3. Anonymous said on January 16, 2017 at 3:16 pm

        Maybe it’s my choice to install them or not but Mozilla has not to recommend me that kind of author.
        In that case mixing “Renaissance” and Religion is confusing, in that case “Recommended” = Proselytizing. JMO.

  12. Dilandu said on January 16, 2017 at 12:14 pm

    Just from the video, correct me if I’m wrong but some capabilities are:
    – Change colors for various parts of the browser; gradients allowed
    – Change button shape
    – Change the appearance of tabs
    – Change the height of UI bars
    – Set a background that can be image or video with sound on blank pages like about:newtab or about:home

    That’s not enough obviously, but:
    – I doubt the video shows everything
    – The theme API is not finished and there’s nothing that says it will not continue to grow even after Firefox 57, if the community pushes for it

    So. Not impressed, but keep going, this is important, a powerful theme API is worth the maintenance cost.

    1. Dilandu said on January 16, 2017 at 12:27 pm


      For future official Firefox themes, take a look at Opera Neon! Some nice things in there.

  13. Jim said on January 16, 2017 at 10:36 am

    Have they released any documentation of the theme API or the code of the example from the video?

    1. Sören Hentzschel said on January 16, 2017 at 6:41 pm

      No, because the videos shows a prototype. The main development just started a few days ago.

  14. Gianni said on January 16, 2017 at 10:24 am

    What does this mean for add-ons like Menu Wizard or LiveClick?

    1. Martin Brinkmann said on January 16, 2017 at 10:26 am

      I don’t know at this point in time. If Mozilla implements the necessary API functions, their authors could create a WebExtensions port.

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