7 Great Firefox about:config Tweaks to Boost Privacy and Performance

If you’ve ever felt like Firefox is holding out on you, like there’s more power hiding under the hood, you’re right. Buried inside Firefox is a hidden settings panel called about:config, and it’s packed with options that the regular settings menu doesn’t even show you. We’re talking privacy controls, network tweaks, memory management, and more.

The good news? You don’t need to be a developer to use it. In this guide, we’ll walk you through 7 of the best about:config tweaks for Firefox in 2026, tested on modern Firefox releases. Whether you’re trying to stop Firefox from tracking you, squeeze out better performance on a low-RAM machine, or just clean up some annoying UI behavior, there’s something here for you.

Note: These tweaks were verified against recent stable Firefox releases. Because Firefox is updated frequently, some preference names or default values may differ depending on your installed version and platform. Always check about:config to confirm a preference exists before changing it.

What Is about:config?

about:config is Firefox’s built-in advanced settings panel. Think of it as the control room that sits behind the regular settings screen. It gives you direct access to hundreds of hidden preferences that you can tweak to change how Firefox behaves. It’s been part of Firefox for years, and it remains fully available in current Firefox releases.

A few things to know before you dive in:

• Some tweaks can break websites if applied carelessly, always change one setting at a time
• You can reset any setting back to its default by right-clicking it and choosing Reset
• Firefox will warn you every time you open about:config that’s normal, just click through it
• For power users: a user.js file in your Firefox profile folder is the cleaner, more permanent way to manage these settings (more on that below)

Before You Begin: Back Up Your Settings

Before you start flipping switches, it’s smart to back up your current Firefox configuration. That way, if something goes sideways, you can restore everything quickly. Here’s how to find your Firefox profile folder, where all your personal Firefox settings live.

Step 1: Open Firefox’s Troubleshooting Page

Type about:support directly into the Firefox address bar and press Enter. This opens the Troubleshooting Information page.

Step 2: Open Your Profile Folder

Under the Application Basics section, look for Profile Folder. Click the Open Folder button next to it (on macOS, this will say Show in Finder).

Step 3: Copy the prefs.js File

In the folder that opens, find the file called prefs.js and copy it somewhere safe. Your Desktop works fine. That file is your backup. If anything goes wrong after tweaking about:config, you can replace the modified prefs.js with your backup copy (while Firefox is closed) to restore your settings.

How to Use about:config

Ready to get in there? Here’s how to access and edit settings in about:config:

1. Type about:config into the Firefox address bar and press Enter.
2. You’ll see a warning page that says you’re entering advanced territory. Click Accept the Risk and Continue.
3. Use the search bar at the top to find any preference by name.
4. To change a value, double-click the preference. For true/false settings, it’ll toggle automatically. For number or text settings, a box will pop up where you can type the new value.
5. Most changes take effect immediately, a few require a browser restart.

Once you’ve changed a setting from its default, it’ll turn bold and show a status of user set. You can sort by that column to see everything you’ve modified at a glance. And if you ever want to undo a change, just right-click the preference and hit Reset.

The 7 Best Firefox about:config Tweaks for 2026

1. Enable Hardcore Tracking Protection

Firefox already blocks a lot of trackers by default, but you can push it further. Before diving into about:config, note that most users will get the best results by first adjusting Enhanced Tracking Protection (ETP) in the standard settings UI: go to Settings > Privacy & Security > Enhanced Tracking Protection and set it to Strict (or use Custom to fine-tune). That’s the easiest and most reliable path for robust tracking protection in modern Firefox.

The about:config preferences below are advanced overrides and checks that work alongside ETP. They can be useful if you want to verify or force specific protections on, but note that their behavior may differ slightly depending on which ETP mode is active. These two settings extend tracking protection to include social media trackers from platforms like Facebook and Twitter that follow you around the web even when you’re not on their sites.

Search for each preference name and double-click it to toggle it to true:

• privacy.trackingprotection.enabled → set to true
• privacy.trackingprotection.socialtracking.enabled → set to true

You probably won’t notice any difference in how pages look, but you’ll be leaking a lot less data to advertisers. Worth it.

2. Disable Telemetry (Stop Firefox From Phoning Home)

By default, Firefox sends usage data back to Mozilla, including things like how you use the browser, crash reports, and health data. If you’d rather keep that to yourself, these three settings will shut it all off:

• toolkit.telemetry.enabled → set to false
• datareporting.healthreport.uploadEnabled → set to false
• browser.ping-centre.telemetry → set to false

Important: For the most reliable telemetry control in current Firefox releases, use the built-in UI option first: go to Settings > Privacy & Security > Firefox Data Collection and Use and uncheck the relevant boxes. The about:config preferences above provide additional granular control, but toolkit.telemetry.enabled and browser.ping-centre.telemetry in particular may be ignored or have no effect in some recent Firefox versions. Always confirm each preference exists in your build before changing it — if a preference is missing, that tweak can be skipped.

These settings stop background data reporting to Mozilla. They are not documented to affect browser performance, though Mozilla designs telemetry to be low-impact regardless.

3. Memory Management for Low-RAM Systems

Got an older laptop or a machine with 8GB of RAM or less? Firefox can be a memory hog, especially with lots of tabs open. These settings help rein it in:

• browser.sessionstore.max_tabs_undo → set to 3 (default is 10; this limits how many closed tabs Firefox remembers, freeing up memory)
• browser.sessionhistory.max_entries → set to 50 (limits how many pages Firefox keeps in your back/forward history per tab)
• image.mem.max_decoded_image_kb → set to 51200 (caps how much memory Firefox uses for decoded images, 51200 = 50MB)

If your system has plenty of RAM, skip this one, modern Firefox is already well-optimized for high-memory machines.

4. Network Optimization for Faster Page Loads (Optional Experiment)

These two settings control how many simultaneous connections Firefox makes to web servers. Bumping them up slightly may help pages with lots of resources (images, scripts, fonts) load a bit faster on fast connections, but results vary by network, server, and system. Treat this as an experiment rather than a guaranteed improvement, and reset to defaults if you notice any slowdown.

• network.http.max-connections → set to 96
• network.http.max-connections-per-server → set to 32

A word of caution: don’t go overboard with max-connections-per-server. Setting it too high can actually get you temporarily rate-limited by some web servers. The values above are a conservative bump. If pages feel slower or you see errors, reset both preferences to their defaults.

5. Clean Up the Address Bar

Firefox’s address bar (called the “Awesome Bar”) has gotten a little… chatty. By default, it shows a grid of top sites every time you click on it, and it auto-expands with suggestions before you’ve even typed anything. If you find that annoying, these two settings clean it up:

• browser.urlbar.openViewOnFocus → set to false (stops the suggestion panel from popping open the moment you click the address bar)
• browser.urlbar.suggest.topsites → set to false (removes the top sites grid from the address bar dropdown)

The address bar will still suggest things as you type. It just won’t ambush you with a wall of suggestions before you’ve started.

6. Smoother Scrolling

If scrolling in Firefox feels a little jerky or abrupt compared to other browsers, this tweak can help. Smooth scrolling makes pages glide rather than jump, and you can also adjust how fast the mouse wheel scrolls:

• general.smoothScroll → set to true (enables smooth scrolling; it may already be on by default)
• mousewheel.default.delta_multiplier_y → set to 200 (increases vertical scroll speed; default is 100, so adjust to taste)

The scroll speed multiplier is personal preference. If 200 feels too fast, try 150. If it still feels too slow, go higher. Just tweak it until it feels right for you.

7. Set a Fixed Disk Cache Size (Optional Experiment)

Firefox’s disk cache stores website files locally so pages load faster on repeat visits. By default, Firefox automatically manages the cache size. You can lock it to a specific size for more predictable behavior, though whether this improves performance depends on your storage speed and browsing habits. If you don’t notice a benefit, you can re-enable smart sizing by setting browser.cache.disk.smart_size.enabled back to true.

• browser.cache.disk.enable → set to true (make sure disk caching is on)
• browser.cache.disk.smart_size.enabled → set to false (disables automatic cache sizing)
• browser.cache.disk.capacity → set to 512000 (sets a 500MB cap on the disk cache)

Note:browser.cache.disk.smart_size.enabled may be deprecated or have no effect in some recent Firefox builds. Confirm the preference exists in your version of about:config before using it – if it’s absent, Firefox is likely managing cache size automatically and this tweak can be skipped.

500MB is a reasonable middle ground for many users. Feel free to adjust based on how much free space you have and whether you notice any difference.

Pro Tip: Use a user.js File for Permanent Tweaks

If you’re planning to apply several of these tweaks, or you want your settings to survive a Firefox profile reset, there’s a smarter way to do it than clicking through about:config every time. It’s called a user.js file, and it’s the method that Firefox power users swear by.

Here’s how it works: you create a plain text file called user.js in your Firefox profile folder, add your preferences in a specific format, and Firefox automatically applies them every time it starts. This is a local, per-installation method. The file itself is not synced by Firefox Sync, so you’ll need to copy it manually to any other device or Firefox profile where you want the same settings.

How to Create a user.js File

Step 1: Find Your Profile Folder

Follow the same steps from the backup section above. Go to about:support and click Open Folder next to Profile Folder.

Step 2: Create the user.js File

In that folder, create a new text file and name it exactly user.js (make sure it doesn’t accidentally save as user.js.txt on Windows, you may need to show file extensions to confirm).

Step 3: Add Your Preferences

Open the file in any text editor (Notepad on Windows, TextEdit on macOS) and paste in your tweaks using this format:

// Firefox 2026 Optimized user.js
// Place in profile folder, restart Firefox

// Privacy
user_pref("privacy.trackingprotection.enabled", true);
user_pref("privacy.trackingprotection.socialtracking.enabled", true);
user_pref("toolkit.telemetry.enabled", false);
user_pref("datareporting.healthreport.uploadEnabled", false);

// Performance
user_pref("network.http.max-connections", 96);
user_pref("browser.sessionstore.max_tabs_undo", 3);
user_pref("image.mem.max_decoded_image_kb", 51200);

// UX
user_pref("browser.urlbar.suggest.topsites", false);
user_pref("general.smoothScroll", true);
user_pref("browser.cache.disk.smart_size.enabled", false);
user_pref("browser.cache.disk.capacity", 512000);

Step 4: Restart Firefox

Close Firefox completely and reopen it. Your settings will be applied automatically. You can verify them in about:config they’ll show as user set.

If you want to go even deeper, check out the arkenfox/user.js project on GitHub. It’s the gold standard for privacy-focused Firefox configuration and is actively maintained.

Tips and Troubleshooting

Common Issues

Problem: A website broke after applying a tweak

This happens sometimes, especially with privacy-related settings. To fix it, go back to about:config, find the preference you changed, right-click it, and select Reset. That’ll restore the default value. Then reload the site.

Problem: My user.js changes aren’t applying

Make sure Firefox is completely closed before you edit the user.js file. If Firefox is still running in the background (check your system tray on Windows), the file won’t be read on the next launch. Close everything, then restart.

Problem: Firefox feels slower after tweaking network settings

Modern Firefox is already highly optimized, so aggressive network tweaks can sometimes backfire. Reset network.http.max-connections and network.http.max-connections-per-server back to their defaults and see if that helps.

Problem: The about:config warning keeps showing up every session

That’s by design. Firefox shows it every time as a reminder that you’re in advanced territory. If you want to skip it permanently, add this line to your user.js file:

user_pref("browser.aboutConfig.showWarning", false);

Quick Reference: All 7 Tweaks at a Glance

Tweak	Preference Name	Value
Tracking Protection	privacy.trackingprotection.enabled	true
Social Tracking Protection	privacy.trackingprotection.socialtracking.enabled	true
Disable Telemetry	toolkit.telemetry.enabled	false
Limit Tab Undo History	browser.sessionstore.max_tabs_undo	3
Network Connections	network.http.max-connections	96
Clean Address Bar	browser.urlbar.suggest.topsites	false
Fixed Cache Size	browser.cache.disk.capacity	512000

Wrapping Up

Firefox’s about:config is still one of the best reasons to use Firefox over other browsers in 2026. No other major browser gives you this level of control without extensions or developer tools. With these seven tweaks, you can lock down your privacy, free up memory, and make the browser feel a little more like yours. And if you want to take it to the next level, setting up a user.js file means you’ll never have to redo your tweaks after a profile reset again.

Start with one or two tweaks that matter most to you. The tracking protection and telemetry ones are great starting points, and you can work your way through the list from there. You’ll be surprised how much difference a few hidden settings can make.