Sorry for the click bait headline but in this case it’s totally true. Let me explain, Firefox only shows you a fraction of its available settings in the interface. If you open a new tab and type about:config in the address bar you will come to a page with hundreds of options.
I have in this article collected the most useful settings in Firefox that you can only find on the about:config page. If you know of a useful setting that is not included in this article please leave a comment below and I will update the article!
browser.ssb.enabled
Set to true to be able to use websites like local apps. Once enabled, after you have restarted the browser, click on the three dots in the address field and then “Use This Site in App Mode”. The will remove the chrome and add the website on your taskbar which makes it look like a local app.
dom.event.contextmenu.enabled
Set to false to prevent websites to block you from accessing the right click menu.
media.autoplay.default
Set to 1 to completely block videos from auto playing. Set to 2 to choose on a domain basis where auto playing should be blocked.
network.IDN_show_punycode
Set to true to show IDN domains as puny code instead. IDN domains let you use non ASCII characters in domain names. This is a problem though since a lot of characters look similar. That makes it possible to have two different domain names that look the same in the address bar. Setting this to true shows the puny code instead which only consists of ASCII characters. You can read more about this attack here.
privacy.userContext.longPressBehavior
This setting is regarding the container feature in Firefox which is a feature I really recommend you check out if you haven’t. If you set this to 2 you get to choose which container you want to open a new tab in if you long press the new tab button. If you set it to 1 you always get the choice.
dom.event.clipboardevents.enabled
This one is my favorite. Have you ever wanted to paste something into a field on a page and the page won’t let you? This stops this behavior. If you set this to false it will prevent the page you are viewing from deciding if you can use copy/paste on that specific page.
network.http.referer.trimmingPolicy
Choose what information is sent in the referrer header.
0 = Everything.
1 = Remove the query string.
2 = Remove query string and path, only send domain name.
browser.backspace_action
If for some reason you can’t go back using the backspace key you should set this to 0 to enable the backspace key.
security.tls.version.max
The highest version of SSL/TLS that you want to use.
4 = TLS 1.3
3 = TLS 1.2
2 = TLS 1.1
1 = TLS 1.0
0 = SSL 3.0
security.tls.version.min
The lowest version of SSL/TLS you want to use. You can use this in combination with the previous setting to limit which SSL/TLS versions you want to use. I have for instance limited myself to TLS 1.2 – 1.3. This setting uses the same 0-4 scale as security.tls.version.max.
browser.urlbar.trimURLs
Set to false to always show http and https in the address bar.
browser.warnOnQuit
Set this to false if you don’t want Firefox to warn you when you close Firefox with multiple tabs open.
widget.content.gtk-theme-override
This setting does not actually exist as standard. You instead have to create it by right clicking on the about:config page and then choose new -> string.
I needed this settings when I started to use a dark theme in Ubuntu. Some elements on websites rendered using the colors of my Ubuntu theme. So there were some dark elements on white pages which caused black text on black background. With this setting you can choose which OS theme Firefox should use to render elements that the website has not specified a style for.
I use the Yuru dark theme so I set this to Yuru which is the default theme and it’s mainly bright/white.
security.enterprise_roots.enabled
Set to True to use the certificate store in the operating system instead of the built in one in Firefox.
browser.autofocus
Block sites from auto focusing on any input fields on the page.
browser.send_pings
Disable hyperlink ping tracking by setting to false.