Advice Request Which Firefox "about:config" setting would you suggest adjusting?

[Halp2001]

I discovered that the recommendations made by the bot are nearly the default settings in Firefox. toolkit.telemetry.enabled = false is locked, and I have no idea why. Does this apply to every Firefox installation?

View attachment 296174

If it shows as 'locked', it’s probably because your Firefox version or a system setting already has it toggled off and secured. Don't worry too much about it; it’s actually a good sign for your privacy, as it means telemetry is 'locked' in the off position and won't be re-enabled by mistake.

 

[bobdoe]

The advice from the Bot and @Marko :) already covers practically all the essentials (especially regarding telemetry and compact mode). To avoid being redundant, I’ll only add a couple of structural isolation tweaks that are key in 2026 and haven't been mentioned yet:

• First-Party Isolation (FPI):privacy.firstparty.isolate = trueThis is the same tech used by the Tor Browser. It creates a "wall" between tabs so sites like Facebook or Google can't track your browsing as you jump to other websites. It’s a massive privacy boost.
• Dynamic Cookie Protection:network.cookie.cookieBehavior = 4This intelligently isolates third-party cookies, preventing them from following you across the web without breaking logins on legitimate sites.

Regarding speed: I agree with the AI Assistant that it’s best not to mess with cache or connection settings (like in post #3). Modern Firefox handles RAM dynamically, and forcing it usually leads to instability or crashes. uBlock Origin remains the #1 "speed" tweak you can have.

Re First-Party Isolation (FPI)... Perplexity says:
First-Party Isolation (FPI) in Firefox is generally not recommended anymore for most users; newer built‑in features like Total Cookie Protection / Dynamic FPI and Network Partitioning have effectively replaced it and are actively maintained, while classic FPI is not.

What FPI Does​

First-Party Isolation makes every site’s storage and identifiers (cookies, cache, etc.) strictly per‑site, preventing one site from reading tracking data set by another. It originated in the Tor Browser and was ported into Firefox mainly to ease Tor’s maintenance, not as a mainstream, fully supported Firefox feature.

Why It’s Not Recommended Now​

• Mozilla support explicitly notes that FPI is “not a supported feature” and suggests disabling it and using Strict Enhanced Tracking Protection (ETP), which enables a dynamic FPI‑like behavior that is supported.
• Privacy‑hardening projects (e.g., arkenfox and community discussions) state FPI has been superseded by Network Partitioning and Total Cookie Protection in Firefox 85+ and that enabling FPI can disable those newer mechanisms and is “no longer maintained” outside Tor.

Practical Downsides of FPI​

• Breakage of third‑party logins (Google, Facebook, some SSO flows) and embedded services; Mozilla’s study found the FPI group hit the most issues of tested privacy settings.
• More annoying CAPTCHAs and friction with services that expect cross‑site state.
• Less efficient caching and higher data usage because shared resources (CDN fonts, JS libraries) get re‑downloaded per site.
• No smooth migration: enabling FPI wipes existing cookies/cache because they weren’t partitioned before.

What To Use Instead​

For a privacy‑focused but usable Firefox setup today, a common recommendation is:

• Leave privacy.firstparty.isolate false.
• Set Enhanced Tracking Protection to Strict, which turns on Dynamic FPI‑style state partitioning / Total Cookie Protection that isolates third‑party storage while keeping better web compatibility.
• Optionally add containers for extra separation of profiles (work vs personal, different logins), which complements but doesn’t replace Firefox’s built‑in state partitioning.

When Might You Still Use FPI?​

You might still consider classic FPI only if:

• You understand that it’s effectively a Tor‑style hardening option, not a mainstream feature.
• You are willing to accept frequent breakage and spend time debugging login and SSO problems.

For most Firefox users, including privacy‑conscious ones, the recommended path is Strict ETP / Total Cookie Protection rather than manually enabling FPI.

 

[Halp2001]

Re First-Party Isolation (FPI)... Perplexity says:
First-Party Isolation (FPI) in Firefox is generally not recommended anymore for most users; newer built‑in features like Total Cookie Protection / Dynamic FPI and Network Partitioning have effectively replaced it and are actively maintained, while classic FPI is not.

What FPI Does​

First-Party Isolation makes every site’s storage and identifiers (cookies, cache, etc.) strictly per‑site, preventing one site from reading tracking data set by another. It originated in the Tor Browser and was ported into Firefox mainly to ease Tor’s maintenance, not as a mainstream, fully supported Firefox feature.

Why It’s Not Recommended Now​

• Mozilla support explicitly notes that FPI is “not a supported feature” and suggests disabling it and using Strict Enhanced Tracking Protection (ETP), which enables a dynamic FPI‑like behavior that is supported.
• Privacy‑hardening projects (e.g., arkenfox and community discussions) state FPI has been superseded by Network Partitioning and Total Cookie Protection in Firefox 85+ and that enabling FPI can disable those newer mechanisms and is “no longer maintained” outside Tor.

Practical Downsides of FPI​

• Breakage of third‑party logins (Google, Facebook, some SSO flows) and embedded services; Mozilla’s study found the FPI group hit the most issues of tested privacy settings.
• More annoying CAPTCHAs and friction with services that expect cross‑site state.
• Less efficient caching and higher data usage because shared resources (CDN fonts, JS libraries) get re‑downloaded per site.
• No smooth migration: enabling FPI wipes existing cookies/cache because they weren’t partitioned before.

What To Use Instead​

For a privacy‑focused but usable Firefox setup today, a common recommendation is:

• Leave privacy.firstparty.isolate false.
• Set Enhanced Tracking Protection to Strict, which turns on Dynamic FPI‑style state partitioning / Total Cookie Protection that isolates third‑party storage while keeping better web compatibility.
• Optionally add containers for extra separation of profiles (work vs personal, different logins), which complements but doesn’t replace Firefox’s built‑in state partitioning.

When Might You Still Use FPI?​

You might still consider classic FPI only if:

• You understand that it’s effectively a Tor‑style hardening option, not a mainstream feature.
• You are willing to accept frequent breakage and spend time debugging login and SSO problems.

For most Firefox users, including privacy‑conscious ones, the recommended path is Strict ETP / Total Cookie Protection rather than manually enabling FPI.

Hi @bobdoe,

I appreciate the input from the "silicon assistant." My suggestions were merely a contribution inspired by @lokamoka820's wonderful curious spirit, not a commandment.

In short, to avoid a long technical debate:

• ETP Strict: This is Mozilla's "smart" way to keep the web functional without breaking logins (dynamic isolation).
• Manual FPI: This is the "bunker mode." It provides deterministic total isolation: cookies, cache, and storage are strictly separated by domain.

The important thing is for everyone to customize their Firefox however they like. In the end, what matters is that we control the browser, and not the other way around.

 

[bobdoe]

Hi @bobdoe,

I appreciate the input from the "silicon assistant." My suggestions were merely a contribution inspired by @lokamoka820's wonderful curious spirit, not a commandment.

In short, to avoid a long technical debate:

• ETP Strict: This is Mozilla's "smart" way to keep the web functional without breaking logins (dynamic isolation).
• Manual FPI: This is the "bunker mode." It provides deterministic total isolation: cookies, cache, and storage are strictly separated by domain.

The important thing is for everyone to customize their Firefox however they like. In the end, what matters is that we control the browser, and not the other way around.

You're welcome.

 

[simmerskool]

I discovered that the recommendations made by the bot are nearly the default settings in Firefox. toolkit.telemetry.enabled = false is locked, and I have no idea why. Does this apply to every Firefox installation?

View attachment 296174

I'm running firefox 148.0 (in freebsd) and opened like yours, but I clicked + on the right and it is not locked, from what I can tell but not 100% sure...

 

[Senkei]

This thread was started 4 years ago.

What settings should be configured for an SSD?

 

[harlan4096]

If You read the thread:

Disable the following settings in about:config

browser.cache.disk.enable - false
browser.cache.disk.smart_size.enabled - false
browser.cache.disk_cache_ssl - false
browser.cache.offline.enable - false
Enable/set the following settings in about:config

browser.cache.memory.enable - true (I believe this is true by default)
browser.cache.memory.capacity - 512000 (that's 500 MB, I actually have mine set to 1 GB)
Check about:cache to make sure that the changes are now reflected.

memory section
Maximum storage size: 512000 KiB
Storage disk location: none, only stored in memory

disk section
Maximum storage size: 512000 KiB

 

[Marko :)]

I discovered that the recommendations made by the bot are nearly the default settings in Firefox. toolkit.telemetry.enabled = false is locked, and I have no idea why. Does this apply to every Firefox installation?

View attachment 296174

I think it's because you disabled the telemetry in Firefox settings. I have this locked as well.

 

[lokamoka820]

This thread was started 4 years ago.

What settings should be configured for an SSD?

As @harlan4096 indicated in his post, I would like to add the following from @Marko's post, which is also very effective:

browser.sessionstore.interval set to 1800000 — reduces writing to SSD, but restoring session won't work great in case Firefox crashes (never happened to me)

I think it's because you disabled the telemetry in Firefox settings. I have this locked as well.

View attachment 296218

In order to verify the default settings, I refreshed my Firefox profile and discovered that it was also disabled. I believe that uBlock Origin modifies some privacy settings, such as turning off prefetching.

 

[Marko :)]

As @harlan4096 indicated in his post, I would like to add the following from @Marko's post, which is also very effective:


In order to verify the default settings, I refreshed my Firefox profile and discovered that it was also disabled. I believe that uBlock Origin modifies some privacy settings, such as turning off prefetching.

I'm not sure extensions have access to about:config section of the Firefox. Or am I mistaken?

 

[lokamoka820]

I'm not sure extensions have access to about:config section of the Firefox. Or am I mistaken?

I'm not sure too, but it has "Read and modify privacy settings" in its "Required permissions" section.

 

[Sampei.Nihira]

Instead of searching for information from four centuries ago (four years in this field are equivalent to centuries), wouldn't it be better to use:

GitHub - yokoffing/Betterfox: Firefox user.js for optimal privacy and security. Your favorite browser, but better.

+ LNA section
+ SSL section (to reduce Insecure Cipher Suites)

 

[Halp2001]

Extensions cannot change the values in about:config. What they actually do is provide a real-time override: Firefox's internal switch remains the same, but the extension instructs the browser to ignore that function while it's active. If you see a setting shown as 'locked' (with a padlock), it’s most likely because you already toggled it in the standard Settings menu, and Firefox locks it in the advanced panel to prevent conflicts.

 

[lokamoka820]

Instead of searching for information from four centuries ago (four years in this field are equivalent to centuries), wouldn't it be better to use:

GitHub - yokoffing/Betterfox: Firefox user.js for optimal privacy and security. Your favorite browser, but better.

+ LNA section
+ SSL section (to reduce Insecure Cipher Suites)

What about updating? Will user.js settings be reset when you update Firefox? Additionally, is it possible for Betterfox user.js to update automatically or do I need to manually check for it?

 

[oldschool]

What about updating? Will user.js settings be reset when you update Firefox? Additionally, is it possible for Betterfox user.js to update automatically or do I need to manually check for it?

I've never used the user.js option. You could use BetterFox only as a reference guide and enable about:config manually. More user input needed but you control your configuration and it's stable, unaffected by browser updates. And then occasionally check the BetterFox web page.

 

[SeriousHoax]

I rarely use Firefox these days but here's my config:

AnythingWindows/Browsers/user.js at main · SeriousHoax/AnythingWindows

Windows Configuration tools and other useful items - SeriousHoax/AnythingWindows

github.com

 

[Sampei.Nihira]

What about updating? Will user.js settings be reset when you update Firefox? Additionally, is it possible for Betterfox user.js to update automatically or do I need to manually check for it?

Of course they remain.
It often happens that some changes in user.js become default in FF, so you won't see them in bold anymore.
However, it's a good idea to check every now and then.
I'm like @oldschool , I do everything the old-fashioned way, manually, but I don't expect everyone to do the same.

 

[lokamoka820]

Of course they remain.
It often happens that some changes in user.js become default in FF, so you won't see them in bold anymore.
However, it's a good idea to check every now and then.
I'm like @oldschool , I do everything the old-fashioned way, manually, but I don't expect everyone to do the same.

Thanks to your link in the previous post, I was able to access the Waterfox configuration files. I used to like this browser because of its default privacy settings, but I stopped using it due to late security updates.

For those who are interested, here is the link: waterfox/waterfox/browser/app/profile at current · BrowserWorks/waterfox

 

[MWTSenior]

The best and must used about:config pref is "ui.textScaleFactor" to fix the UI scaling on devices with high DPI scaling and screen resolution.

 

[lokamoka820]

The "Block AI Enhancement" killswitch in the "AI Controls" section of the Firefox settings eliminates a lot of bloat and restores Firefox to its proper state.