Mozilla launches Site Compatibility Tools for Firefox

Martin Brinkmann
Aug 7, 2019
Updated • Aug 7, 2019
Firefox, Firefox add-ons

Site Compatibility Tools is a new extension for the Firefox web browser designed to find and report site compatibility issues experienced in Firefox.

If you take Internet Explorer and the old Microsoft Edge out of the picture, as they are not the focus of development anymore, you are left with Firefox and Safari when it comes to browsers with a sizeable user base that are not based on Chromium.

With Chrome's huge market share on the desktop, it is becoming a trend seemingly that certain websites or services don't work well in Firefox or not at all. Google plays a role here certainly, as it is not uncommon to find the company block browsers from accessing updated products or services, or even new ones, at least for a period of time.

A few examples: the new Google Earth release of 2017 was Chrome exclusive, the new Chromium-based Microsoft Edge was blocked from accessing the new YouTube, or accusations that Google made YouTube slower for other browsers deliberately.

Mozilla is very aware of the implications; the organization launched several projects and initiatives to tackle the issue from different angles. It launched a Web Compatibility page in Firefox recently that lists changes that Firefox makes to certain sites to get them to display and work properly in the browser.

Site Compatibility Tools

firefox site compatibility tools

Site Compatibility Tools is another tool that has just been released. Web developers are the main audience but anyone may download and install the extension.

The first version of the extension supports reporting functionality and provides site compatibility news for Firefox versions. Mozilla plans to extend that in the future by integrating a site compatibility checker in the extension. Once launched, it would give webmasters and developers a tool at hand to test websites for compatibility issues directly in Firefox.

The extension is compatible with all recent versions of the Firefox web browser. Launch the Developer Tools after installation and switch to the Compatibility tab to display its set of tools.

It starts with a list of site compatibility changes in different Firefox versions. The links point to Mozilla's Firefox Compatibility Site and provide further information on the change.

The only other feature that is available in the initial release version is the reporter. It displays options to report problems with sites to Mozilla via Twitter (openly or via direct message), GitHub, or by using email. It is a rudimentary feature at the time of writing.

Firefox users may report issues to Mozilla using the Web Compatibility reporter as well. It is linked in Nightly but can be accessed directly as well.

Closing Words

The initial version of the Site Compatibility Tools extension has limited uses; this will change when compatibility checking is integrated into the extension as it may help developers find issues on webpages and sites in an automated process.

Now You: What is your expectation in this regard? Can Mozilla keep up with compatibility issues?

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Site Compatibility Tools
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  1. bla said on August 8, 2019 at 8:15 am

    I’m curious why it is that all main browsers choose to be based on Chromium (Blink) in stead of Firefox. Is it because the Mozilla codebase is difficult to work with?

    I’m aware of a few Firefox forks (Palemoon, Waterfox, IceCat) but as far as I know they use older versions (pre-Quantum) or run behind in other ways (except IceCat perhaps).

    1. Yuliya said on August 8, 2019 at 11:48 pm

      Chromium is more modern, performance scales better on modern multicore machines, faster in most situations, better support for modern web standards, backed up by a large team, who actually knows what they are doing.
      I remember asking Opera developers on the old MyOpera blogs when I first heared that they were about to switch to Chromium. My question was why Chromium instead of Firefox. It’s also probably easier to work with Chromium as a base – a base which barely changed since its release. Chromium is very simple with very little options natively, which means no future changes should affect your alterations which you’ve added on top of it. Firefox on the other hand… v4, v28 (or was it v38 with the australis abomination?), v57; not to mention addons used to break from one version to another. It’s not a reliable project, it’s barely being held into place with sticky tape and super glue at this point. It’s a wonder this thing still compiles…

    2. Iron Heart said on August 8, 2019 at 10:29 am


      Web developers mainly test their website on Chromium-based browsers these days, as those already have 80%+ market share. Why bother to test for 15% of users who might as well switch to Chrome.

      In the beginning, Chrome had way better development tools than Firefox, which is why most web devs chose Chrome for their daily work early on. Mozilla has improved the dev tools in Firefox now, but IMHO too little, too late. They are still no match for Chrome’s dev tools. Say about Google what you will, but their Chrome team certainly knows exactly what it is doing on a technical level.

  2. Stan said on August 7, 2019 at 8:35 pm

    “no relation between the usefulness of such an add-on and the market share”


    Bravo ! Comedic comment of the day!

    @Someone needs to tell MozCo there no longer is a ‘community’, we were screwed, now it’s time for them to learn actions have consequences.

  3. Johnny said on August 7, 2019 at 8:11 pm

    Yes, I agree, a Chromium mono culture is not good.
    But that battle was lost when microsoft chose chromium over firefox for their new edge.

    The thing is…, chromium is now the new battle ground for the browser wars!

    1. Iron Heart said on August 8, 2019 at 8:52 am

      100% agree, whether you like or dislike Mozilla, I think the only realistic outlook is that Firefox won’t regain a substantial market share again. I even expect Apple to switch to Blink eventually.

  4. T said on August 7, 2019 at 7:32 pm

    Just heads up that this blog post is wrong, this is not a Mozilla initiative. See the extension description:

    “The Firefox Site Compatibility Working Group is an independent community initiative tackling the backward compatibility and regressions in Firefox. We are creating this browser extension as a handy all-in-one tool for web developers to learn, check and report site compatibility issues directly within Firefox Developer Tools.”

  5. Johnny said on August 7, 2019 at 9:42 am

    This is proof that firefox is becoming irrelevant.
    Their market share is so small that web devs don’t bother anymore to test on firefox!

    Hence the need for this extension for pursuing compatibility with websites instead of the websites pursuing compatibility with firefox.

    1. Tom said on August 7, 2019 at 2:27 pm

      > This is proof that firefox is becoming irrelevant.

      Nothing new on ghacks – article about something from Mozilla and immediately the bashing starts in the comments section.

      Needless to say that this “argument” doesn’t make sense at all because there is no relation between the usefulness of such an add-on and the market share. Such an extension for Chrome would also make a lot of sense, even with the big market share of Chrome.

    2. Yuliya said on August 7, 2019 at 11:05 am
      1. Ngamer01 said on August 7, 2019 at 7:07 pm

        We’re back in the IE6 era, but with Chrome/Chromium this time. If only Mozilla execs would get their heads out of their butts and start innovating instead of following Google.

        I’m pretty much expecting Mozilla to dump Gecko/Servo and switch to a Chrome/Chromium engine soon. I wish somebody would just buy out Mozilla or at least buy the rights to Phoenix/Firefox so that somebody can do what Mozilla used to do (support their users instead of themselves).

    3. Martin Brinkmann said on August 7, 2019 at 10:13 am

      I think it is one of Mozilla’s attempts to get the community involved to detect and fix as many compatibility issues as possible to avoid mass exodus from Firefox to a Chromium-based browser. It is without doubt a problem and I cannot see it getting better unless something drastic happens.

      1. Johnny said on August 7, 2019 at 1:41 pm

        The typical browser user doesn’t want that burden. He wants to browse the web and the websites to just work on whatever browser he chooses.
        If mozilla wants to put the burden of detecting and reporting website incompatibilities on the average browser user, it’s only gonna loose them faster!

        I’ve used firefox for over a decade, but with the constant erosion of it’s identity, the features that made it unique, and the constant process throughout the years of chromification, I left for a chromium based browser – Vivaldi.

        Right now probably the best mozilla can do is move firefox to chromium based, effectively ending website incompatibilities right there, while maintaining and even getting back many of the UI configurability and flexibility that it had.

      2. Martin Brinkmann said on August 7, 2019 at 2:02 pm

        Yes that is correct. Users just want the browser to work. I don’t think that a Chromium monoculture would be all that great; we already see Google starting to use its muscles and not all the time for the better of the Web or people.

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