For the more advanced, you can also mess around with the userChrome.css file. To create it open a text editor and save the file as userChrome.css in the \Chrome folder in your Firefox profile folder* (make sure to restart Firefox to apply the changes)

To enable the file, enter about:config in the address bar, then accept the warning if it appears. Search for toolkit.legacyUserProfileCustomizations.stylesheets and double-click it to set it to true.

*enter about:support in the address bar, or click on the Help menu > More Troubleshooting Information, then scroll to the Profile Folder line and click on Open Folder. Usually it’s C:\Users\~USERNAME~\AppData\Roaming\Mozilla\Firefox\Profiles\~PROFILENAME~

*Note: the first 2 lines about tab height might not work if you don’t have the Playing/Muted text line in tabs disabled. To disable that line go to about:config, search for browser.tabs.secondaryTextUnsupportedLocales, and add ,en (or the relevant language that you’re using in your system) at the end of the value for it then click Enter and restart Firefox to apply the change.

Here’s the userChrome I use (compiled from different sources)

/*    Tabs/Tab Bar height    */
:root {
 --tab-min-height: 20px !important;
 --tab-max-height: 20px !important;
}

/*    Menu Bar height    */
#toolbar-menubar {
  margin-top: 0px !important;
  margin-bottom: 0px !important;
  padding-top: 0px !important;
  padding-bottom: 0px !important;
  line-height: 22px !important;
  max-height: 22px !important;
}
/* Fixing title bar buttons (close/min/max) due to shortened Menu Bar height */
#toolbar-menubar .titlebar-button {
  padding-block: 1px !important;
}

/* toolbar/address bar/url bar height  */
/* https://github.com/CarterSnich/firefox-xtra-compact/blob/master/chrome/userChrome.css */
toolbar#nav-bar {
	max-height: 30px !important;
}
hbox#urlbar {
	min-height: 22px !important;
}
hbox#urlbar:not([focused="true"]) {
	max-height: 22px !important;
}

/*    Menu Items height/padding    */
menupopup > menu, /* this is the sub-menus/folders/containers */
menupopup > menuitem {
  padding-block: 3px !important; /* above and below each item */
  margin-left: 0px !important; /* margin is the outer space around an item */
  padding-left: 8px !important; /* padding is the inner space inside an item */
  margin-right: 0px !important;
  padding-right: 7px !important; /* otherwise some text in menus gets cut off with ellipses */
}

/* the padding of the menu itself */
menupopup {
  --panel-padding: 1px !important;
}

/* the text part of the item/sub-menu */
menupopup > menu > hbox, /* this is the text part of the sub-menus/folders/containers */
menupopup > menuitem > hbox {
  margin-left: 0px !important;
  margin-right: 8px !important; /* otherwise some text in menus gets cut off with ellipses */
}


menuseparator {
  padding-block: 0px !important;
}

:root{
--arrowpanel-menuitem-padding: 1px 1px !important;
--arrowpanel-menuitem-margin-inline: 1px !important;
--arrowpanel-menuitem-padding-block: 1px !important;
--panel-separator-margin-horizontal: 1px !important;
--panel-subview-body-padding-block: 1px !important;
}
/*(The 2nd number in the first line refers to the left side and right side of the item)*/


/*    Spacing/padding around addons icons in the toolbar/urlbar    */

:root {
  --toolbarbutton-outer-padding: 0px !important;
  --toolbarbutton-inner-padding: 7px !important;
}

.toolbaritem-combined-buttons:not([widget-type='button-and-view']),
.toolbaritem-menu-buttons {
  margin-inline: 0px !important;
  margin-inline-start: 0px !important;
  margin-inline-end: 0px !important;
}

#tabs-newtab-button {
  padding-left: 3px !important;
}

Sorry, it was unclear in my comment. By “it’s actually part of the Mozilla Corporation” I was referring to Firefox, not Mozilla Foundation

for anybody that wants to disable it, go to the settings and search for “Allow websites to perform privacy-preserving ad measurement”

(or through the dom.private-attribution.submission.enabled flag in about:config)

https://support.mozilla.org/en-US/kb/privacy-preserving-attribution

for anybody that wants to disable it, go to the settings and search for “Allow websites to perform privacy-preserving ad measurement”

(or through the dom.private-attribution.submission.enabled flag in about:config)

https://support.mozilla.org/en-US/kb/privacy-preserving-attribution

Just adding that as I understand this, donations to the Mozilla Foundation cannot go towards Firefox, because it’s [edit: Firefox is] actually part of the Mozilla Corporation. To help with funding Firefox people can consider purchasing the Corporation’s other products (VPN/Relay/Monitor), or purchasing merch.

See more here on the AMA on Reddit, and this thread

• Lights: Switching to light sources/bulbs with lower brightness/warmer light temperature (lower Kelvin/K-value) 3 hours before bed. (Light affects our sleep-wake cycle, aka the circadian rhythm. Our brain processes bright light as “the sun is still up so it’s not time to sleep yet”)
• Screens: Gradually dimming electronic screens until bedtime (Computer: using F.lux and lowering the brightness gradually in the graphics card’s control panel. Phone: with a built-in Night/Dark Mode option that you can schedule or by using an app like Twilight). // Don’t take your devices to the bedroom, or keep them far away from the bed and set them on silent/shut them off.
• Try not to sleep for more than 8 hours so you’ll need the sleep the next night.
• Sleeping in a closed and completely dark room (including covering LED lights on electronics, or using a face mask) with something that makes a white noise (fan/air purifier/etc.)
• Food: Having a light meal 3-3.5 hours before bed and light snacks 1.5-2 hours before bed, to not put the body into overdrive digesting a heavy meal or cause heartburn/indigestion, and also to not go to sleep hungry and get distracted by that.
• If you sleep on your stomach with your head to the side, you can use a thin and narrow side pillow (but firm) along your torso to support your shoulder on the side that your head is pointing to. (you can also use a thin pillow for your head to not strain your neck/spine - there are ones made for kids if needed)

• Lights: Switching to light sources/bulbs with lower brightness/warmer light temperature (lower Kelvin/K-value) 3 hours before bed. (Light affects our sleep-wake cycle, aka the circadian rhythm. Our brain processes bright light as “the sun is still up so it’s not time to sleep yet”)
• Screens: Gradually dimming electronic screens until bedtime (Computer: using F.lux and lowering the brightness gradually in the graphics card’s control panel. Phone: with a built-in Night/Dark Mode option that you can schedule or by using an app like Twilight). // Don’t take your devices to the bedroom, or keep them far away from the bed and set them on silent/shut them off.
• Sleeping in a closed and completely dark room (including covering LED lights on electronics, or using a face mask) with something that makes a white noise.
• Food: Having a light meal 3-3.5 hours before bed and light snacks 1.5-2 hours before bed, to not put the body into overdrive digesting a heavy meal or cause heartburn/indigestion, and also to not go to sleep hungry and get distracted by that.
• If you sleep on your stomach with your head to the side, you can use a thin and narrow side pillow (but firm) along your torso to support your shoulder on the side that your head is pointing to. (you can also use a thin pillow for your head to not strain your neck/spine - there are ones made for kids if needed)

On the humorous side:

• My Brother, My Brother And Me - 3 brothers giving not-so-serious advice to listeners, reacting to questions from Yahoo Answers (when that was a thing), and later adding other segments, and overall being funny/silly (note: sometimes they make references that go over my head, but they’re still enjoyable. These references might be best enjoyed by midwestern Americans who grew up in the late 80’s/early 90’s)
• My Dad Wrote A Porno - 3 people reacting to an “erotica” book series that one of the guys’ dad published (I would say the books are maybe only 5%-20% explicit, depending on the chapter) (some of the characters’ voices can be annoying/grating, and the narrator tends to repeat sentences after they react to them which can be annoying as well)
• No Such Thing As A Fish - the behind-the-scenes staff of the show QI bring up interesting facts and tidbits from history/nature/etc. (each episode is split into 4 parts where each member brings up a fact and the others react to it and bring up related facts)
• If I Were You - Jake & Amir from CollegeHumor giving advice to listeners (mostly in a sarcastic/tongue-in-cheek way but sometimes genuinely), mostly about relationships/dating
• SmartLess - Jason Bateman and Will Arnett (Arrested Development) and Sean Hayes (Will & Grace) interview a famous person each episode where only one of the hosts known who it is beforehand (it gets better after the first few episodes, though some conversations are less funny/entertaining than others)
• Conan O’Brien Needs A Friend - Conan interviews a famous person each episode (I like the interview part better than the introduction, and similarly to Smartless some conversations are less funny than others)
• If you watched The Office (US) - Office Ladies - Jenna and Angela from the show reacting to each episode of the show and bringing up behind-the-scenes stuff (some of episodes include interviews with other cast members/staff) (might not be as humorous as the others but still fun to listen to)

On the humorous side:

• My Brother, My Brother And Me - 3 brothers giving not-so-serious advice to listeners, reacting to questions from Yahoo Answers (when that was a thing), and overall being funny/silly
• My Dad Wrote A Porno - 3 people reacting to an “erotica” book series that one of the guys’ dad published (I would say the books are maybe only 5%-20% explicit, depending on the chapter) (some of the characters’ voices can be annoying/grating, and the narrator tends to repeat sentences after they react to them which can be annoying as well)
• No Such Thing As A Fish - the behind-the-scenes staff of the show QI bring up interesting facts and tidbits from history/nature/etc. (each episode is split into 4 parts where each member brings up a fact and the others react to it and bring up related facts)
• If I Were You - Jake & Amir from CollegeHumor giving advice to listeners (mostly in a sarcastic/tongue-in-cheek way but sometimes genuinely), mostly about relationships/dating
• SmartLess - Jason Bateman and Will Arnett (Arrested Development) and Sean Hayes (Will & Grace) interview a famous person each episode where only one of the hosts known who it is beforehand (it gets better after the first few episodes, though some conversations are less funny/entertaining than others)
• Office Ladies - Jenna and Angela from The Office (US) reacting to each episode of the show and bringing up behind-the-scenes stuff (some of episodes include interviews with other cast members/staff)

Pro- the SSD will live longer
Con- the RAM will fill up more, especially when opening resource-heavy pages (though there’s a way to unload inactive tabs so that might not be that big of a deal, and especially if you have enough RAM to spare)

Personally I’ve been using memory-only cache for about a decade (half on HDD, half on SSD) and I don’t think I’ve noticed any adverse effects from that. (though I rarely have more than 5 tabs open at once)