Firefox 66: The Sound of Silence

Firefox 66 is out, and brings with it a host of great new features like screen sharing, scroll anchoring, autoplay blocking for audible media, and initial support for the Touch Bar on macOS.

These are just highlights. For complete information, see:

Audible Autoplay Blocking

Starting with version 66, Firefox will block audible autoplaying video and audio. This means media (audio and video) have to wait for user interaction before playing, unless the muted property is set on the associated HTMLMediaElement. Blocking can be disabled on a case-by-case basis in the site information overlay:

Screenshot of the Site Information panel showing the 'Autoplay sound' permissionNow you get to decide when to disturb the sound of silence.

Note: We’re rolling out blocking gradually to ensure that it doesn’t break legitimate use cases. All Firefox users should have blocking enabled within a few days.

Usability Improvements

Scroll Anchoring

Firefox now implements scroll anchoring, which prevents slow-loading content from suddenly appearing and pushing visible content off the page.

Touch Bar

The Touch Bar on macOS is now supported, offering quick access to common browser features without having to learn keyboard shortcuts.

Photo of Firefox's buttons on a MacBook Pro Touch Bar

Tab Search

Too many tabs? The overflow menu sports a new option to search through your open tabs and switch to the right one.

Screenshot of Firefox's tab overflow menu showing a new 'Search Tabs' optionsAstute users will note that clicking on “Search Tabs” focuses the Awesomebar and types a % sign in front of your query. Thus, while the menu entry makes tab search much more discoverable, you can actually achieve the same effect by focusing the Awesomebar and manually typing a % sign or other modifier.

Extension Shortcuts

Speaking of shortcuts, you can now manage and change all of the shortcuts set by extensions by visiting about:addons and clicking “Manage Extension Shortcuts” under the gear icon on the Extensions overview page.Screenshot of Firefox's new settings page to manage keyboard shortcuts added by extensions

Better Security Warnings

We’ve completely redesigned Firefox’s security warnings to better encourage safe browsing practices (i.e., don’t ignore the warnings!)

Expanded CSS Features

Firefox is the first browser to support animating the CSS Grid grid-template-rows and grid-template-columns properties, as seen in the video below.

We’re also the first browser to support the overflow-inline and overflow-block media queries, which make it possible to apply styles based on whether (and how) overflowing content is available to the user. For example, a digital billboard might report overflow-block: none, while an e-reader would match overflow-block: paged.

Furthermore, Firefox now supports:


The new getDisplayMedia API enables screen sharing on the Web similarly to how getUserMedia provides access to webcams. The resulting stream can be processed locally or shared over the network with WebRTC. See Using the Screen Capture API on MDN for more information.Screenshot of Firefox's screen sharing dialog

Mozilla is using getDisplayMedia in Bugzilla to allow people to take and attach screenshots to their bug reports, directly from inside the browser.

Also, starting with Firefox 66, InputEvent now has a read-only property, inputType. This distinguishes between many different types of edits that can happen inside an input field, for example insertText versus insertFromPaste. To learn more, check out the documentation (and live demo) on MDN.

Browser Internals

Lastly, we’ve made a few changes to how Firefox works under the hood:

From all of us at Mozilla, thank you for choosing Firefox!

About Dan Callahan

Engineer with Mozilla Developer Relations, former Mozilla Persona developer.

More articles by Dan Callahan…


  1. Boris Bosanovici

    Yes, but does it have a multirow bookmarks add-on, like the old 56 which the entire internet is actually still using because of that ?

    March 20th, 2019 at 15:00

    1. Dan Callahan

      It does not. WebExtensions do not have the same ability to modify Firefox’s interface as legacy Add-Ons.

      Running an old browser places your computer and your data at great risk. If you’re unable to upgrade Firefox, then please consider switching to another browser that you are willing to keep up to date.

      March 21st, 2019 at 10:18

      1. Glenn

        Why does Firefox put a white background behind printed pages, even though (1) IE & Edge don’t (2) HTML specifies a default transparent background (3) I specify a transparent background? I tried to find where it does that in the code, but found it extremely hard to figure out the printing code. Can someone point me to where that happens, so I can try to patch it? This is particularly troublesome when trying to merge captured print files together. Looking at captured PDF output files shows big page-size white blocks that are not part of the HTML on the page.

        March 21st, 2019 at 13:11

        1. Dan Callahan

          If you don’t mind wrestling with Bugzilla, it’s probably best to file an issue and follow up there. It’d be especially helpful if you could give pedantically detailed steps to reproduce what you’re seeing; there are a lot of moving parts. :-)

          If you do file a bug, please come back here and comment with the bug number so I track it.

          March 21st, 2019 at 13:54

          1. Glenn

            Oh, I did the bug thing a year ago… Bug 1432750 … and after a bit, tried to wade through the printing code… seems there is a huge learning curve required to actually understand the printing code, though…

            I was surprised that FF has a setting for background color in Options, but I couldn’t find an option for transparency there, either.

            March 21st, 2019 at 14:43

  2. Jerry

    Audible Autoplay Blocking, is a major improvement now that many sites have allowed audio advertisements to load and play after you have scrolled past them. The only way you can stop them is scroll back trying to find the offending file.

    March 21st, 2019 at 07:19

  3. jop

    Oh my god THANK YOU for being the first to get grid-template animation out the door. It seems like something that should have shipped with the original spec, but nonetheless, it’s an incredible tool to be able to resize individual elements like that and I can’t wait to go back and add it to those use cases I’ve wanted to for a long time

    March 21st, 2019 at 07:30

  4. Juan Lanus

    I noticed that the screenshots are made with macs.
    Is that the OS used by the great majority of Firefox users?

    March 21st, 2019 at 07:55

    1. Dan Callahan

      The vast majority of Firefox users are on Windows, but macOS and Linux are very popular among Firefox developers.

      March 21st, 2019 at 10:11

  5. Greg

    Does this version take up less ram than the previous ones? If not, are there any plans to make the browser less of a ram hog? I really love Firefox, but the ram usage makes it impractical at times.

    March 21st, 2019 at 15:59

    1. Dan Callahan

      The memory overhead per tab was reduced, but we used that budget to double the maximum number of processes that Firefox runs for web content. This means you probably won’t see much of a difference if you usually have many tabs open, but your Firefox should have better and more consistent performance thanks to the additional processes.

      There are ongoing projects to further improve Firefox’s memory footprint, which you can read about in the second bullet under “Browser Internals” above.

      March 22nd, 2019 at 14:38

  6. Sergey Kuzmenko

    Mozilla have a VPN?

    March 22nd, 2019 at 02:23

    1. Dan Callahan

      We do not currently have a VPN offering, though we did test a partnership with ProtonVPN last year.

      March 22nd, 2019 at 14:40

  7. Stager

    Can’t use 66. Could not get Flash working. Without Flash I consider FF 66, or any browser, crippled. I don’t care how much sugar you add, once you piss in it by pulling Flash, I absolutely DO NOT WANT IT.

    March 23rd, 2019 at 13:34

    1. Dan Callahan

      Flash should still work in Firefox, however you should be aware that Flash is a dead end. Next year, Adobe will stop distributing Flash, and all browsers will completely remove support. See our press release and deprecation roadmap from last year for more information.

      If you still rely on websites that use Flash, please encourage the authors to upgrade to modern Web standards.

      March 23rd, 2019 at 13:51

      1. Rumi

        I can’t get Flash to work in Firefox 66 either (linux). Plugin says it is up to date, Firefox says its there and working. But any flash content tells me there is no flash player installed.

        And to the smug developers who always say “just don’t use flash” or “upgrade to modern web standards” let me remind you that there are millions of dollars of software apps that have been developed based on Flash – particularly in education – that are not online and not on a website. These apps are written, done, paid for, and will not be recoded on a new platform. The money simply isn’t there. Yes we know flash is on its way out but there is absolutely nothing we can do about it. So in the meantime, we have to do ridiculous things like install old version of Firefox and immediately take the computers offline to keep the browsers from upgrading and ruining it…

        March 25th, 2019 at 11:28

        1. Dan Callahan

          I believe you need to manually enable Flash on a per-site basis. There should be an icon to the left of the URL that appears and allows you to unblock Flash. You might also want to check its settings in the Plugins tab of about:addons (is it set to Never Activate by mistake?)

          I understand that “upgrade to web standards” isn’t very satisfying, but is inevitable: Adobe themselves will stop distributing Flash next year, and there’s nothing we can do about that either.

          You can at least avoid the rush to take computers offline by using the DisableAppUpdate Policy to prevent Firefox from auto-updating. Of course, disabling updates creates security risk. If you do enable that policy, please ensure that you do only use that copy of Firefox with internal, trusted content.

          March 26th, 2019 at 15:14

  8. Rai42

    I very much appreciate how you are working against the internet cancer that is intrusive advertising. Thank you.

    However, after the feature was announced in february, it was promised that there would be an option to block silent autoplaying as well
    (here: )

    Where can I find this option now in FF 66.0 on Linux? It only has a “Block websites from automatically playing sound” checkbox.

    Also, about:config settings that I had previously made to do exactly that have apparently stopped working. Videos (e.g. on twitter) have started to (silently) autoplay again.

    March 24th, 2019 at 06:16

    1. Dan Callahan

      There isn’t yet a visible checkbox for disabling even muted autoplay, but you should be able to solve that in about:config:

      1. Make sure media.autoplay.default is set to 1 (this is the “Block websites from automatically playing sound” preference, which will be on by default for everyone in just over a week.)

      2. Set media.autoplay.allow-muted to false (this prevents all media from autoplaying, even if muted.)

      3. Optionally, set image.animation_mode to “none” or “once” if you also want to disable animated GIFs.

      CSS animations and animations driven by HTML5 canvas / WebGL will likely continue to play, and I’m not aware of any straightforward ways to prevent that.

      March 24th, 2019 at 08:24

      1. Rai42

        Thanks for the quick reply.

        I already had settings #1 and #2, and #3 does not seem to help either.

        However, I noticed that the problem doesn’t occur everywhere, and is possibly specific to Twitter. Twitter likes to autostart videos as they are scrolled into view, and FF currently does not prevent this. Not sure if the videos fall into the category you mention, but it previously worked on Twitter, so something has changed. Does FF consider scrolling enough “user interaction” to allow autoplay? I don’t think it should. If the video is already in view when the page is loaded, it does not autoplay.

        Video example:
        (scroll down, then up again => video starts playing).

        March 24th, 2019 at 10:28

        1. Dan Callahan

          Hi, apologies for the slow reply this time. :-)

          In my testing, scrolling alone did not allow autoplay on that Twitter link (and I could see the autoplay blocked message in the console every time the video scrolled back into view, so I’m certain it was working). How are you scrolling?

          I’ve observed that any click inside the page is enough to denote user attention and thus disable blocking. I once caught myself instinctively clicking the empty space to the side of the timeline before scrolling the page, which subtly re-enabled autoplay. Similarly, scrolling by hitting the space bar also counts, though the page up / page down and arrow keys do not.

          March 26th, 2019 at 14:48

  9. happysurf

    Will be super great have in the bottom panel, in the Permissions section the possibility of allow cookie or not per site.

    March 26th, 2019 at 00:52

    1. Dan Callahan

      There is a “Cookies” overview under Content Blocking in the site information panel that lets you see what domains are setting / being prevented from setting cookies. Actually managing this on a site-by-site basis is a very advanced feature that is probably best left to add-ons.

      On the topic of cookies, I’ve been quite happy with first-party isolation, which separates third party cookies based on the current domain visible in the URL bar. For example, if two sites use the same analytics provider, you get two separate cookies: one for each site. This keeps cookies working within sites, but prevents them from tracking you across sites.

      March 26th, 2019 at 15:04

  10. LetsPlayNintendoITA

    this should be an option that has to be disabledable cause i don’t like it enabled and have to actually click on the play button when i play youtube videos IT’S ANNOYING!!!!!!!!! FIX please

    March 31st, 2019 at 09:11

    1. Dan Callahan

      It is an option. Search for “autoplay” in preferences. Uncheck the box labeled “Block websites from automatically playing sound.”

      April 1st, 2019 at 07:57

  11. Lenny

    @Dan, Is it possible to customize the layout of the touch bar?
    Over the past few days since upgrading, I find myself accidentally touching the “refresh” button as I type. (pretty often, I’m embarrassed to say)

    April 3rd, 2019 at 22:23

    1. Dan Callahan

      Hi Lenny! We don’t yet support a GUI for customizing the Touch Bar (that’s Bug 1522012), but you can change things by editing the ui.touchbar.layout property in about:config. Changes to that property require a restart to take effect.

      You can see the list of all available buttons in MacTouchBar.js. Currently that’s: Back, Forward, Reload, Home, Fullscreen, Find, NewTab, Sidebar, ReaderView, OpenLocation, and Share.

      April 4th, 2019 at 08:00

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