Tuning Firefox Quantum

Firefox Quantum (aka the current Firefox as of 2018) is a good browser but it has also a dark side. It is pre-fetching content, it's contacting all kinds of servers on the internet and it can easily overwhelm older computers or low bandwidth internet connections.

I love older Thinkpads because of the ergonomics. The trackpoint and the keyboards of those machines are second to none. To get firefox to work well on those machines I change the following. The settings apply to Firefox version 60 and up. In future some of those features in Firefox might change and I do not plan to update this article but it will give you some ideas even in a few years down the road as to where to look.

All of my settings are done in "about:config". Yes, it is OK to accept that waring:

Firefox has a number of accessibility features to attach devices for visually impaired and they take just memory and cpu cycles if you don't need them
accessibility.force_disabled;1
Firefox makes now extensive use of a CPU multiprocessor architecture but this can be bad for older laptops with just one or two CPU cores. This setting could make firefox slower on newer computers. You have to try it and see what the effect is.
browser.tabs.remote.autostart;false
Firefox builds a huge disk cache. If you are concerned about SSD wear then you can simply move that cache to ram. You can see cache use by typing "about:cache" into firefox. Note that some browser plugins might have a problem with this setting.
browser.cache.disk.enable;false
browser.cache.memory.enable;true (might be already true)
browser.cache.memory.capacity;5000 (cache size in kilo bytes)
If start Firefox without going to any page then you will see (netstat -anp | more) that it does already establish a dozened connections to places like yul03s05-in-f3.1e100.net (that's google) and ec2-54-201-6-28.us-west-2.compute.amazonaws.com or similar. This is all related to blocklists and speculative pre-fetching based on your start page or bookmarks. I think such features have almost no benefit and are more akin to spyware and malware.
extensions.blocklist.enabled;false
network.prefetch-next;false
network.dns.disablePrefetch;true
network.http.speculative-parallel-limit;0
If you don't use the "firefox pocket" offline reading feature then just disable it and save cpu power:
extensions.pocket.enabled;false
Firefox has this account and remote bookmark feature but even if you don't use it it will call home unless your set the following:
identity.fxaccounts.enabled;false
Videos that play automatically are a big problem and it is highly recommended to disable this. The following will cause firefox to ask if videos are allowed to start playing automatically. It will block video autoplay by default and ask for your permission.
media.autoplay.default;2
Almost nobody uses ipv6 for internet access. To try to use ipv6 makes no sense. Disable DNS lookup for ipv6:
network.dns.disableIPv6;true
Firefox will do a DNS lookup on every url/domain found in a given page hoping that you might click on one of them. This is a lot of processing for almost no gain especially if you have a good local DNS cache on your computer:
network.dns.disablePrefetch;true
Firefox will call home to keep track of how often you use it. If you don't like that then set:
network.captive-portal-service.enabled;false
Firefox has a feature called safebrowsing where it reports everything that you do to google in order to see if this is "safe". There is no reason to use this unless you hang out on strange sites.
Search for browser.safebrowsing.*.enabled
and make sure all of them are set to false
Firefox has a feature called Heartbeat that is responsible for "Please Rate Firefox" and "Your Firefox is critically out of date". You disable this with:
extensions.shield-recipe-client.enabled
and set to false

Firefox on modern high dpi displays, tiny font, strange look

Firefox might look strange on screens with a very high resolution. The font will appear tiny but just increasing the font will still make it look strange. Here is a setting for firefox on high dpi/hi res displays:
layout.css.devPixelsPerPx=1.5

Must have addons for Firefox

It is increasingly important to defend yourself against blinking advertisement and other annoying things when you read an otherwise interesting document. Add blockers are too heavy weight and they need to update and download blocklists all the time. Here are two addons that to a pretty good job on most pages and they are generic.

https://addons.mozilla.org/en-US/firefox/addon/disable-javascript/, Javascript is important for the web. Some services like paypal don't work without it. On many sites were you just want to read the text it is really helpful to switch Javascript off. This addon does it on a per domain bases.
https://addons.mozilla.org/en-US/firefox/addon/nuke-anything-enhanced/, This is a really cool addon it allows you to remove any element from a web page. Just click the little "radio active icon" and then move the mouse over the area that you want to remove. Press x to remove elements. Press Esc when done. You can edit anything. On some sites you can even remove pay-wall overlays. I use it mostly to prepare a web page for printing to remove bulky banners and useless page footers that would just cost unnecessary ink.

Firefox, plugin disabled, May 2019 bug

There is a rather embarrassing bug related to the expiry date of the certificate used by mozilla to sign plugins. A lot of plugins got disabled in May 2019 because somebody at mozilla was asleep at the wheel.

You can read about it here: https://blog.mozilla.org/addons/2019/05/04/update-regarding-add-ons-in-firefox/ and here: https://hacks.mozilla.org/2019/05/technical-details-on-the-recent-firefox-add-on-outage/.

A simple fix that works for a number of firefox versions is to set the parameter xpinstall.signatures.required to false.

Update 2020-07-12: Firefox, disable checks for updates

As of firefox 7x you will need to create a policies.json file in the install directory of firefox within a subdirectory called distribution. This file must contain:

{
"policies": {
"DisableAppUpdate": true 
}
}

Example:
You installed firefox in the directory /opt/firefox-76.0.1 (the firefox binary is then /opt/firefox-76.0.1/firefox-bin ).

create a directory called distribution: mkdir /opt/firefox-76.0.1/distribution
go to that directory and create the file policies.json with the above content:
cd /opt/firefox-76.0.1/distribution
vi policies.json
restart the browser

You can check if your browser understood the policy by typing about:policies in the URL bar.

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