121 votes
Accepted

All of my Firefox add-ons have been disabled suddenly, how can I re-enable them?

The Problem An intermediate signing certificate, used by Mozilla to sign add-ons, has expired. This causes Firefox to consider add-ons signed with that certificate to be untrusted. The issue is being ...
  • 998
104 votes

How to hide tab bar (tabstrip) in Firefox 57+ Quantum

Open your firefox "profile directory" Official docs how to do that: https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data#w_how-do-i-find-my-profile Or just open: ...
  • 3,276
58 votes

How to get the Markdown Viewer addon of Firefox to work on Linux?

Happy to report that I was able to find a solution that I provided here: https://github.com/Thiht/markdown-viewer/issues/62#issuecomment-277702230 I've also copied it here for reference: On Linux, ...
  • 781
54 votes

All of my Firefox add-ons have been disabled suddenly, how can I re-enable them?

The intermediate code signing certificate expired. This means that all add-ons signed with the cert are no longer trusted. In this case the browser is doing it's job. Mozilla will need to get the ...
  • 495
43 votes
Accepted

Firefox shortcut to open a particular account container

As of version 7 of the Containers extension, ctrl+shift+1-9 works without any further add-on. From the release notes: Set shortcuts in the add-on preferences panel: Ctrl + Shift + {Num} Which ...
  • 868
40 votes

Firefox shortcut to open a particular account container

According to the Multi-Account Container plugin page, you can use Ctrl + . to open the panel. Then simply press the down arrow (or tab) and enter. Ctrl + . (period) keyboard shortcut is available ...
  • 501
38 votes
Accepted

Firefox Quantum (ver >= 57) - How Can I Hide the Horizontal Tab Bar with TreeStyle Tabs?

The horizontal tab bar can be hidden with the following steps: Confirm or Create: Linux: ~/.mozilla/firefox/<profile name>/chrome/userChrome.css Windows: %AppData%\Mozilla\Firefox\Profiles\<...
  • 995
34 votes
Accepted

Change Firefox new tab background

I think this may interest others as well. ANSWER UPDATE (as of 2020) By now there's a lot of cool and interesting addons that do the job in great way, let me mention some of my favorite in a brief ...
  • 1,904
26 votes
Accepted

Remove a site from its default Firefox container

There is a way to do this without dropping the container. You must go to the Multi-account container button in the top bar, then click to manage containers, then click the container where the wrong ...
  • 491
20 votes

How to configure firefox built-in pdf viewer

Mozilla have now implemented a default zoom setting, although it's only available through about:config. You can change the pdfjs.defaultZoomValue in about:config to change the default zoom. Set it to ...
  • 313
20 votes
Accepted

How to force install an unverified firefox extension in 41.0b1+?

Yes, there is a setting in About:config, its name is xpinstall.signatures.required. Double-click on the preference name so that its value is set to false. Now you can install unsigned extensions in ...
  • 419
19 votes

Change key bindings (keyboard shortcuts) in Firefox Quantum

There is a way. It's not super official, but basically you can unpack browser/omni.ja, edit the keybindings in chrome/browser/content/browser/browser.xul, repack it, delete startup cache and it will ...
  • 329
17 votes
Accepted

How to examine source code of Firefox extension before installing it?

To check a Firefox extension source before installing. This works on macos and linux. Got to e.g. https://addons.mozilla.org/en-US/firefox/addon/open-same-tab/ Right click "+ Add to Firefox"...
  • 306
17 votes
Accepted

How to force to restart firefox in a clean way?

Update: Now it is possible to do it directly in the url bar, asking for the special page about:restartrequired about:restartrequired It opens a page with a button to restart firefox that should ...
  • 18.1k
16 votes

Change Firefox new tab background

Open about:config and change the value browser.display.background_color to the color of your choice. I'm using #595959 (neutral gray). This works with blank tab or "Firefox Home". Sadly, opening ...
  • 1,053
15 votes

How to hide tab bar (tabstrip) in Firefox 57+ Quantum

I want the tab bar to auto hide when there's 1 tab and appear when there's multiple. Not the same as the question but this is about the only Google result right now for 57+ so for those who need it in ...
  • 191
14 votes

How do I prevent pages I visit from overriding selected Firefox shortcut keys?

Since Firefox 58 it is possible to disable keyboard shortcuts override per web site. "Override Keyboard Shortcuts" and many other permissions are available in "Page Info -> Permissions" (under info ...
13 votes

Unblocking at element-level in uBlock Origin

For folks looking how to unblock elements they manually added themselves, you can click the uBlock icon, click the gear icon in the top left corner to go into the 'dashboard'. From there, go to the '...
  • 131
13 votes

Is there a Chrome equivalent for Firefox's multi-account container extension?

I recommend Switch Multi-Account Login for Chrome/Chromium. It's the best alternative have found.
12 votes

How to examine source code of Firefox extension before installing it?

As Wladimir pointed out the .xpi file is simply a ZIP archive put together in a particular way. Open it with WinRAR, 7-zip or rename it to .zip and open it with your OS's default tool. EDIT: (It ...
12 votes
Accepted

How to enable a proxy in Firefox only for some URLs and not for every page I visit?

I had a similar requirement and found two solutions to the problem: If you do not mind paying for the service use FoxyProxy Plus. The free version of FoxyProxy should also work fine for this. You can ...
  • 236
12 votes

All of my Firefox add-ons have been disabled suddenly, how can I re-enable them?

This issue is due to a mass expiration of add-on certificates. As others have mentioned, a fix is in the works. To temporarily re-enable add-ons, you can navigate to about:config and set xpinstall....
  • 837
11 votes
Accepted

How to prevent automatic update to Firefox 57.0 Quantum?

The solution to disable automatic updates without running Firefox is as follows (OS is Windows): Edit the file prefs.js, located in %APPDATA%\Mozilla\Firefox\Profiles\xyz.default\ which usually ...
  • 1,247
11 votes
Accepted

How to make Firefox 57 to always open new tab from address bar?

Firefox 60 actually has flag browser.urlbar.openintab in about:config. Setting it to true accomplishes what you want. Tried and true.
11 votes

Is there a Chrome equivalent for Firefox's multi-account container extension?

There is SessionBox, but it does not have the exact same features, I am afraid. "Firefox Multi-Account Containers" is the only reason why I use Firefox.
  • 111
10 votes

How can I auto-select the spellcheck language in Firefox?

Software in general is unfriendly to us bilingual users. No web browser offers this functionality built-in. Some operating systems do, however. For example, on the Mac, switching your keyboard layout ...
  • 787
10 votes
Accepted

Unblocking at element-level in uBlock Origin

You can use the uBlock Origin's own logger for logging the network requests that got blocked or allowed in addition to the CSS rules that were affected by your filters. Please assist this official ...
  • 455
9 votes

All of my Firefox add-ons have been disabled suddenly, how can I re-enable them?

I found another way to get the hotfix. It's the same fix as above, but tinkering with settings trying to get Studies to download failed to get it on my machine. I found a GitHub issue that described ...
  • 631
8 votes

How to hide tab bar (tabstrip) in Firefox 57+ Quantum

Add to <firefox-profile-dir>/chrome/userChrome.css #TabsToolbar { visibility: collapse; } #titlebar { margin-bottom: -22px !important; } #titlebar-buttonbox { height: 0px !...
  • 300
7 votes

How can I spell check web pages from the browser?

In Chrome, open the console by pressing Ctrl + Shift + J. In the console, type the following and hit Enter. document.body.contentEditable = true; document.designMode = 'on'; This will make the page ...

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