Here are some Firefox tweaks I did to improve my daily browser experience.

copy/paste

I hate websites that block the password copy/paste or even some of them block the email confirmation.

A lot of people, or at least some people, use passwords vaults to be able to copy/paste their 64+ characters passwords without having to type them.

In Firefox, there is an option in the about:config url :

dom.event.clipboardevents.enabled 

that you should disable and put to false

search tab

By default, the search tab loads the results in the current tab. To change that behaviour, you can change that by enabling this to true :

browser.search.openintab 

number of content processes

I always have a lot of tabs open, sometimes more than 250 of links that I want to read later. I try to treat myself and now I use wallabag, an opensource free alternative to Pocket, but I still have a lot of links to read.

The more content processes you have, the more CPU it wil use for each tab.

dom.ipc.processCount 8 

I keep this one to the default one 8 but you can modify it depending on number of tabs you have between 8 and 12.

browser width

I have a lot of tabs open and I hate them when they're too small because you can't see what the page is. A good thing is that you can change the width tab value :

 browser.tabs.tabMinWidth 120

The default is 76 but I like it a little bit wider and I use 120.

add-ons quick install

There is a delay when you install add-ons for some reasons that I don't understand. You can cut that delay changing this value :

security.dialog_enable_delay 10

The default value is 1000 ms, I changed that to 10.

zoom

When you zoom, Firefox remembers sites where you increased/decreased default values. If you want to always have the same zoom preference for all your sites, you should changed the next parameter to false :

browser.zoom.siteSpecific true

disable animations

New versions of Firefox bring some little animations that are eating your RAM. You can disable them by setting the next value to false :

toolkit.cosmeticAnimations.enabled false