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{{Note|The trailing slash on {{ic|/dev/snd/}} is important, otherwise apulse will report "Permission denied" errors.}}
=== Dictionaries for spell checking ===
=== Dictionaries for spell checking ===

Revision as of 20:07, 3 October 2017

Firefox is a popular open-source graphical web browser from Mozilla.


Firefox can be installed with the firefox package. For printing support, see Gtk#Printers not shown in the GTK print dialog.

Other alternatives include:

  • Firefox Extended Support Release — long-term supported version
https://www.mozilla.org/firefox/organizations/ || firefox-esrAUR or firefox-esr-binAUR
  • Firefox Beta — cutting-edge version
https://www.mozilla.org/firefox/channel/desktop/#beta || firefox-betaAUR or firefox-beta-binAUR
  • Firefox Developer Edition — for developers
https://www.mozilla.org/firefox/developer/ || firefox-developerAUR or firefox-devAUR
https://www.mozilla.org/firefox/channel/desktop/#nightly || firefox-nightlyAUR
  • Firefox KDE — Version of Firefox that incorporates an OpenSUSE patch for better KDE integration than is possible through simple Firefox plugins.
https://build.opensuse.org/package/show/mozilla:Factory/MozillaFirefox || firefox-kde-opensuseAUR

Here you can find an overview of Mozilla's releases.

There are a number of language packs available for Firefox, other than the standard English. Language packs are usually named as firefox-i18n-languagecode (where languagecode can be any language code, such as de, ja, fr, etc.). For a list of available language packs see this.


Firefox is well known for its large library of add-ons which can be used to add new features or modify the behavior of existing features of Firefox. You can find new add-ons or manage installed add-ons with Firefox's "Add-ons Manager."

For a list of popular add-ons, see Mozilla's add-on list sorted by popularity. See also List of Firefox extensions on Wikipedia.

Adding search engines

Search engines can be added to Firefox through normal add-ons, see this page for a list of available search engines.

A very extensive list of search engines can be found at the Mycroft Project.

Also, you can use the add-to-searchbar extension to add a search to your search bar from any web site, by simply right clicking on the site's search field and selecting Add to Search Bar...


Install the arch-firefox-search package to add Arch-specific searches (AUR, wiki, forum, etc, as specified by user) to the Firefox search toolbar.


Firefox exposes a number of configuration options. To examine them, enter:


in the Firefox address bar.

Once set, these affect the user's current profile, and may be synchronized across all devices via Firefox Sync. Please note that only a subset of the about:config entries are synchronized by this method, and the exact subset may be found by searching for services.sync.prefs in about:config. Additional preferences and 3rd party preferences may be synchronized by creating new boolean entries prepending the config value with services.sync.prefs.sync (documentation is still applicable.) To synchronize the whitelist for the extension NoScript:


The boolean noscript.sync.enabled must be set to true to synchronize the remainder of NoScript's preferences via Firefox Sync.

Firefox also allows configuration for a profile via a user.js file: user.js kept in the profile folder, usually ~/.mozilla/firefox/xxxxxxxx.default/. For a useful starting point, see e.g custom user.js which is targeted at privacy/security conscious users.

One drawback of the above approach is that it is not applied system-wide. Furthermore, this is not useful as a "pre-configuration", since the profile directory is created after first launch of the browser. You can, however, let firefox create a new profile and, after closing it again, copy the contents of an already created profile folder into it.

Sometimes it may be desired to lock certain settings, a feature useful in widespread deployments of customized Firefox. In order to create a system-wide configuration, follow the steps outlined in Locking preferences:

1. Create /usr/lib/firefox/defaults/pref/local-settings.js:

pref("general.config.obscure_value", 0);
pref("general.config.filename", "mozilla.cfg");

2. Create /usr/lib/firefox/mozilla.cfg (this stores the actual configuration):

//...your settings...
// e.g to disable Pocket, uncomment the following line
// lockPref("browser.pocket.enabled", false);

Please note that the first line must contain exactly //. The syntax of the file is similar to that of user.js.

Multimedia playback

Firefox uses FFmpeg for playing multimedia inside HTML5 <audio> and <video> elements. Go to YouTube's HTML5 page, video-test page or audio-test page to check which formats are actually supported.

HTML5 DRM playback is supported by the Google Widevine CDM, it is however not enabled by default. See Preferences > Content > DRM content if you want to learn more.

See Firefox tweaks#Enable additional media codecs for advanced configuration and enabling support for Widevine (Netflix, Amazon Video, etc.).

Starting with version 54, Firefox uses PulseAudio for audio playback and capture. For sound to work, you need to install the pulseaudio package.

In case, for whatever reason, PulseAudio is not an option for you, you can use apulse instead. To make this work, it is necessary to exclude /dev/snd/ from Firefox' sandboxing by adding it to the comma-separated list in about:config:

Note: The trailing slash on /dev/snd/ is important, otherwise apulse will report "Permission denied" errors.

Dictionaries for spell checking

To enable spell checking for a specific language right click on any text field and check the Check Spelling box. To select a language for spell checking to you have right click again and select your language from the Languages sub-menu.

To get more languages just click Add Dictionaries... and select the dictionary you want to install from the list.

Alternatively, you can install the hunspell package. You also need to install dictionaries for your language, such as hunspell-fr (for the French language) or hunspell-he (for Hebrew).

By default, Firefox will try to symlink all your hunspell dictionaries in /usr/lib/firefox/dictionaries. If you want to have less dictionaries offered to you in Firefox, you can remove some of those links. Be aware that it may not stand an upgrade of Firefox.

When your default language choice does not stick, see #Firefox does not remember default spell check language.

KDE/GNOME integration

  • To bring the KDE look to GTK apps (including Firefox), install breeze-gtk and kde-gtk-config. Afterwards, go to System Settings > Application Style > GTK. Be sure to choose 'Breeze' in 'Select a GTK2/GTK3 Theme' and check 'Show icons in GTK buttons' and 'Show icons in GTK'.
  • For integration with KDE’s mime type system and file dialogs, one can use firefox-kde-opensuseAUR variant from AUR with OpenSUSE’s patches applied.
  • Install mozilla-extension-gnome-keyring-gitAUR (all-JavaScript implementation) to integrate Firefox with GNOME Keyring. To make firefox-gnome-keyring use your login keychain, set extensions.gnome-keyring.keyringName to "login" (without the double quotes) in about:config. Note the lowercase 'l' despite the the keychain name having an uppercase 'L' in Seahorse.
  • To make the left mouse button warp the scrollbar instead of the middle one on KDE, go to System Settings > Application Style > GTK and set the checkbox for "Left mouse button warps scrollbar".


Note: Firefox has removed support for NPAPI plugins, except for Flash. Firefox ESR will support plugins until 2018.

See the main article: Browser plugins

To find out what plugins are installed/enabled, enter:


in the Firefox address bar or go to the Add-ons entry in the Firefox Menu and select the Plugins tab.

Tips and tricks

For general enhancements see Firefox/Tweaks, for privacy related enhancements see Firefox/Privacy.

Screenshot of webpage

To use Firefox to take a screenshot of a webpage open the developer console using Shift+F2. Then type in:

screenshot filename

where filename is optional.

To take a screenshot of the entire page, not just the section displayed on the screen, use the --fullpage option:

screenshot --fullpage filename


Firefox startup takes very long

If Firefox takes much longer to start up than other browsers, it may be due to lacking configuration of the localhost in /etc/hosts. See Network configuration#Local network hostname resolution on how to set it up.

Font troubleshooting

See Font configuration.

Firefox has a setting which determines how many replacements it will allow from fontconfig. To allow it to use all your replacement-rules, change gfx.font_rendering.fontconfig.max_generic_substitutions to 127 (the highest possible value).

Setting an email client

Inside the browser, mailto links by default are opened by a web application such as Gmail or Yahoo Mail. To set an external email program, go to Preferences > Applications and modify the action corresponding to the mailto content type; the file path will need to be designated (e.g. /usr/bin/kmail for Kmail).

Outside the browser, mailto links are handled by the x-scheme-handler/mailto mime type, which can be easily configured with xdg-mime. See Default applications for details and alternatives.

File association

See Default applications.

Firefox keeps creating ~/Desktop even when this is not desired

Firefox uses ~/Desktop as the default place for download and upload files. To change it to another folder, set the XDG_DESKTOP_DIR option as explained in XDG user directories.

Make plugins respect blocked pop-ups

Some plugins can misbehave and bypass the default settings, such as the Flash plugin. You can prevent this by doing the following:

  1. Type about:config into the address bar.
  2. Right-click on the page and select New > Integer.
  3. Name it privacy.popups.disable_from_plugins.
  4. Set the value to 2.

The possible values are:

  • 0: Allow all popups from plugins.
  • 1: Allow popups, but limit them to dom.popup_maximum.
  • 2: Block popups from plugins.
  • 3: Block popups from plugins, even on whitelisted sites.

Middle-click errors

A common error message you can get while using the middle mouse button in Firefox is:

The URL is not valid and cannot be loaded.

Another symptom is that middle-clicking results in unexpected behavior, like accessing a random web page.

The reason stems from the use of the middle mouse buttons in UNIX-like operating systems. The middle mouse button is used to paste whatever text has been highlighted/added to the clipboard. Then there is the possibly conflicting feature in Firefox, which defaults to loading the URL of the corresponding text when the button is depressed. This can be easily disabled by going to about:config and setting the middlemouse.contentLoadURL option to false.

Alternatively, having the traditional scroll cursor on middle-click (default behavior on Windows browsers) can be achieved by searching for general.autoScroll and setting it to true.

Backspace does not work as the 'Back' button

According to mozillaZine, the Backspace key was mapped based on which platform the browser was running on. As a compromise, this preference was created to allow the Backspace key to either go back/forward, scroll up/down a page, or do nothing.

To make Backspace behave like the back button type about:config in the address bar and search for the property browser.backspace_action, then set it to 0.

You can also set the property browser.backspace_action to 1 so the Backspace key will scroll up the page, whereas Shift+Backspace scrolls down. Setting this property to any other value will leave the key unmapped (Arch Linux defaults to 2, in other words, it is unmapped by default).

Firefox does not remember login information

It may be due to a corrupted cookies.sqlite file in Firefox's profile folder. In order to fix this, just rename or remove cookie.sqlite while Firefox is not running.

Open a terminal of choice and type the following:

$ rm -f ~/.mozilla/firefox/<profile id>.default/cookies.sqlite

The profile id is a random 8 character string.

Restart Firefox and see if it solved the problem.

Unreadable input fields with dark GTK+ themes

Merge-arrows-2.pngThis article or section is a candidate for merging with Firefox tweaks#Appearance.Merge-arrows-2.png

Notes: Anything on that page might be in troubleshooting section as well, so let us keep the info in one place. (Discuss in Talk:Firefox#)

When using a dark GTK+ theme, one might encounter Internet pages with unreadable input and text fields (e.g. Amazon can have white text on white background). This can happen because the site only sets either background or text color, and Firefox takes the other one from the theme. The extension Text Contrast for Dark Themes sets the other color as needed to maintain contrast.

Another workaround is to explicitly setting standard colors for all web pages in ~/.mozilla/firefox/xxxxxxxx.default/chrome/userContent.css or using stylish add-on.

The following sets input fields to standard black text / white background; both can be overridden by the displayed site, so that colors are seen as intended:

Note: If you want urlbar and searchbar to be white remove the two first :not css selectors.
input:not(.urlbar-input):not(.textbox-input):not(.form-control):not([type='checkbox']):not([type='radio']) {
    -moz-appearance: none !important;
    background-color: white;
    color: black;

#downloads-indicator-counter {
    color: white;

textarea {
    -moz-appearance: none !important;
    background-color: white;
    color: black;

select {
    -moz-appearance: none !important;
    background-color: white;
    color: black;

Alternatively, force Firefox to use a light theme (e.g. "Adwaita:light"):

  1. Copy /usr/share/applications/firefox.desktop to ~/.local/share/applications/firefox.desktop and replace all occurrences of Exec=firefox with Exec=env GTK_THEME=Adwaita:light firefox.
  2. Close all running instances of Firefox and restart your window manager/desktop environment.

"Do you want Firefox to save your tabs for the next time it starts?" dialog does not appear

From the Mozilla support site:

  1. Type about:config in the address bar.
  2. Set browser.warnOnQuit to true.
  3. Set browser.showQuitWarning to true.

Silently fails when installing desktop apps from marketplace

Installation of apps from Firefox OS Marketplace will silently fail if there is no ~/.local/share/applications folder.

Firefox detects the wrong version of my plugin

When you close Firefox, the latter saves the current timestamp and version of your plugins inside pluginreg.dat located in your profile folder, typically in ~/.mozilla/firefox/xxxxxxxx.default/.

If you upgraded your plugin when Firefox was still running, you will thus have the wrong information inside that file. The next time you will restart Firefox you will get that message Firefox has prevented the outdated plugin "XXXX" from running on ... when you will be trying to open content dedicated to that plugin on the web. This problem often appears with the official Adobe Flash Player plugin which has been upgraded while Firefox was still running.

The solution is to remove the file pluginreg.dat from your profile and that is it. Firefox will not complain about the missing file as it will be recreated the next time Firefox will be closed. [1]

Javascript context menu does not appear on some sites

In about:config, unset the dom.w3c_touch_events.enabled setting.

Firefox does not remember default spell check language

The default spell checking language can be set as follows:

  1. Type about:config in the address bar.
  2. Set spellchecker.dictionary to your language of choice, for instance en_GB.
  3. Notice that the for dictionaries installed as a Firefox plugin the notation is en-GB, and for hunspell dictionaries the notation is en_GB.

When you only have system wide dictionaries installed with hunspell, Firefox might not remember your default dictionary language settings. This can be fixed by having at least one dictionary installed as a Firefox plugin. Notice that now you will also have a tab Dictionaries in add-ons.

Related questions on the StackExchange platform: [2], [3], [4]

Related bug reports: Bugzilla 776028, Ubuntu bug 1026869

Some MathML symbols are missing

You need some Math fonts, namely Latin Modern Math and STIX (see this MDN page: [5]), to display MathML correctly.

In Arch Linux, these fonts are provided by texlive-core and texlive-fontsextra, but they are not available to fontconfig by default. See TeX Live#Fonts for details. You can also try other Math fonts.

Picture flickers while scrolling

Tango-inaccurate.pngThe factual accuracy of this article or section is disputed.Tango-inaccurate.png

Reason: Most likely a driver issue, useless without reference (Discuss in Talk:Firefox#)
Note: Problem available in some MATE desktops

Uncheck the "Use smooth scrolling" setting in Edit > Settings > Advanced > General.

Tearing video in fullscreen mode

If you are using the Xorg Intel or Nouveau drivers and experience tearing video in fullscreen mode, try Firefox tweaks#Enable OpenGL Off-Main-Thread Compositing (OMTC).

Firefox looks bad with GTK+ >=3.20

Note: Firefox has removed GTK2 support in version 53 and will support an ESR 52 version until mid 2018.

Firefox (as of version 47) does not support GTK+ >=3.20 and may look unsightly as a result. A possible resolution is compiling Firefox against GTK2 instead, see firefox-esr-gtk2AUR. Alternatively, you may use the archlinuxcn repository (x86_64 only) for pre-built GTK2 Firefox packages.

Firefox WebRTC module cannot detect a microphone

WebRTC applications for instance Firefox WebRTC getUserMedia test page say that microphone cannot be found. Issue is reproducible for both ALSA or Pulseaudio setup. Firefox debug logs show the following error:

$ NSPR_LOG_MODULES=MediaManager:5,GetUserMedia:5 firefox
[Unnamed thread 0x7fd7c0654340]: D/GetUserMedia  VoEHardware:GetRecordingDeviceName: Failed 1

You can try setting media.navigator.audio.full_duplex property to false at about:config Firefox page and restart Firefox.

This can also help if you are using the PulseAudio module-echo-cancel, and Firefox does not recognise the virtual echo canceling source.

Make Firefox 54 use more than one "Web content" process

Tango-go-next.pngThis article or section is a candidate for moving to Firefox/Tweaks.Tango-go-next.png

Notes: Not a troubleshooting. Explain why 4 is better than 1 along the way. (Discuss in Talk:Firefox#)

Firefox 54 supports multiple "Web Content" processes but the default installation uses only one. To solve that, go to about:config and set dom.ipc.processCount to 4. The recommended maximum is four, but you can set up to seven. [6] [7]

With dom.ipc.processCount set to 1 (Default):

# ps -e | grep 'Web Content'
13421 tty1     00:00:14 Web Content

With dom.ipc.processCount set to 4:

# ps -e | grep 'Web Content'
13991 tty1     00:00:04 Web Content
14027 tty1     00:00:09 Web Content
14031 tty1     00:00:20 Web Content
14040 tty1     00:00:26 Web Content

See also