The new Firefox design lands in today. This is what you can expect

[AshleyT]

Firefox has evolved significantly over the past year and now, its look has evolved too. 

The design begins rolling out today, with Firefox 157, bringing a cleaner, more cohesive , and more adaptable experience. It is still the Firefox you know and trust, with the same commitment to independence, privacy, customization, and user control. 

The Mozilla Connect community has helped shape this work from the beginning by sharing feedback on the early designs, tested the experience in Nightly starting in July, filed bugs, and shared with us what worked and what didn’t.

Here’s what landed today.

A cleaner, more cohesive design

• Softer tab shapes
• Redrawn icons that hold up better across light and dark themes
• Rebalanced spacing throughout the interface
• A refreshed color palette featuring the glow of the active tab, deeper purples, and warmer light tones

The updated design brought bolder color choices to Firefox — and your feedback made clear that opinions on browser color run the full spectrum. In response, we created additional themes, accessible through add-ons and a new theme picker off Firefox Home, so you have greater control over how Firefox looks. 

More ways to make Firefox yours

Firefox is becoming more customizable, giving you more ways to shape the browser around how you browse. These options include:

• A new theme picker in the customization panel on the Firefox Home page. Additional community themes remain available through about:addons.
• New Firefox themes and wallpapers
• A dedicated space to pin and organize shortcuts so sites you use all the time stay put.
• Compact Mode for a denser browsing experience

Compact mode now officially supported!

Compact Mode is now available as its own dedicated setting. It will also switch on automatically on smaller screens, reducing the space between interface elements so more fits on the screen.

This is one of the clearest examples of how community feedback shaped Nova. Many of you told us that maintaining a denser interface was important, and we listened.

Faster performance

The refreshed experience also includes improvements to Firefox’s startup, page-loading, and scrolling speeds.

Frequently asked questions

Will my existing themes and add-ons continue to work?

Themes and add-ons should continue to work. Nova is built on the same Firefox foundation, and the extension and theming architecture has not changed.

Will my userChrome.css customizations continue to work?

Some customizations may require minor adjustments, depending on how closely they rely on element names or layout structures from the previous interface. 

But keep in mind that Mozilla does not officially support customizations made through userChrome.css. They can cause unexpected behavior or even break Firefox, and future updates may affect them as Firefox continues to evolve. If you choose to use userChrome.css, please proceed carefully.

You can learn more in Firefox advanced customization and configuration options.

Can I opt out of the update?

The new Firefox design becomes the default experience starting with Firefox 157. However, you have several ways to adjust how Firefox looks and feels, including Compact Mode, themes, wallpapers, and New Tab customization. 

Keep shaping Firefox with us

Nova may be shipping today, but the work doesn’t stop here. Many of these updates grew directly from the bugs you filed and the conversations you started while the design was being developed.

Update to Firefox 157 to try the refreshed experience, then let us know what works well and what could still be improved. Your feedback will continue to help shape what comes next.

[JNavas]

> just rollback and try better again.

Or at least make it a Settings option indefinitely.

[dftf]

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@JackNotParrot wrote:

Why don't you accept users' feedback? People doesn't like Nova, you did bad, just rollback and try better again.

---

You do realise I'm just a user here, not a Mozilla employee? 😝

[Agentvirtuel]

Bonjour

About, browser.nova.enabled
(e.g.) https://support.mozilla.org/en-US/questions/1611802

In this discussion thread, https://connect.mozilla.org/t5/discussions/feedback-on-the-new-ui-corner-rounding-dark-theme-and-win..., i voted.

To complement, https://connect.mozilla.org/t5/firefox-labs/firefox-updates-force-closes-tabs-and-ms-docs-lost-legal...
https://www.youtube.com/watch?v=wIwTxJjiPkI

css
https://support.mozilla.org/en-US/questions/1610048
https://support.mozilla.org/en-US/questions/1611680#answer-1855268

[JackNotParrot]

Hi everyone!

I have been using Firefox since 2005, it's my main browser all the time and I'm a big fan of it. What I think about new Firefox 157 UI design if anyone cares? It's awful. Not only does it look really bad (which it does), but it also hurts UX: thin tabs, big spaces, big paddings, etc... wastes screen space.

I find the redesigned UI less comfortable and less practical than the previous version. Instead of improving my daily browsing experience, it forces me to adapt to visual changes that I neither requested nor find beneficial.

browser.nova.enabled=false works fine for me now, but I'm not sure how long this will last

Please keep classic Firefox interface as officially supported option for your users.

[cadwellm]

Unfortunately, I've read the option to change Nova in about:config is supposed to be removed around November 24th of this year.

[JNavas]

The best solution to the ugly, less functional Nova UI (at least for the next year) is to switch from regular Firefox to Firefox ESR (Extended Support Release), which retains the classic Proton UI and is also more stable. See Navas' Tips: Firefox UI Debacle

[JackNotParrot]

Firefox ESR is a good option, but anyway it's support time is limited. So, I think another decent alternative is a classic Theme (if it's made from original css-s we can keep now, it should be good enough). 

But anyways I think, that denying users the freedom to choose goes against the Firefox philosophy.

[JNavas]

An ESR release gets a year of updates, but that's not necessarily the end of the ESR trail, because we don't know how good or bad a future ESR version will be.

ESR has the further benefit of being more stable than the standard release, which is being compromised by rapid updates.

We are still free to choose, standard or ESR, or another browser entirely.

[dftf]

ESR 153.5 is a good option for now, though the final update for it is planned to be 153.27, due for release September 7th next-year.  So at that-point, if Mozilla haven't backtracked on Nova, or offered supported ways to reverse the UI, when users move onto ESR 175.6 on September 21st, they'll be back to Nova and no about:config option to undo it.

So perhaps the next topics on your blog could be you trying-out some of the most-common forks of Firefox and seeing which currently offer an older UI, and importantly a pledge to retain that UI?

[JNavas]

> So perhaps the next topics on your blog could be you trying-out some of the most-common forks of Firefox and seeing which currently offer an older UI, and importantly a pledge to retain that UI?

I think that's premature, since these forks may follow the Nova UI in the future, and if they don't, then security fixes may be an issue (a major concern in this new age of AI attacks).

[dftf]

Security-issues won't automatically occur just because some forks may choose to retain an older UI; as long as they still pay attention to the code that renders the UI.

Though could a website realistically hack into your PC via an exploit in the Firefox UI renderer?  I wouldn't think code on webpages can interact it with it directly, beyond the APIs they get presented for that, enabling stuff like disabling the right-click menu, preventing text-selection or changing the colour of, or hiding, the scrollbar.

But outside of a possible malicious theme extension, not sure this is a big worry?

The more-pressing security issue with forks is: how quickly in-general do they import security-fixes from upstream Firefox?  For example, there is a cool Chromium browser called "Min" (https://github.com/minbrowser/min/releases) that has a very scaled-back UI; but the last update to it was August 23rd.  It's now October 16th, meaning we're nearly eight-weeks on now, and some security issues fixed in Chrome (and major Chromium derivatives, like Brave, Edge, Opera and Vivaldi), won't be there yet. 😬

[JNavas]

• Forks and patch lag: We agree on the delay risk. Your example with Min highlights the exact problem. When a fork freezes a legacy UI while upstream keeps moving, backporting fixes becomes exponentially harder. Firefox's UI (the chrome) runs in the privileged parent process. When upstream Mozilla refactors IPC mechanisms, DOM security boundaries, or internal APIs, merging those security updates into a frozen, diverged UI is a recipe for merge conflicts, broken security assumptions, and missed patches.

• Can a website compromise the host through the UI? Yes. Web pages run in a sandboxed content process, but the UI runs in the parent process with full OS privileges. Real-world drive-by compromises rely on exploit chains: an attacker uses a web-level vulnerability (e.g., in the JS engine) to execute code in the sandbox, and then exploits IPC bugs or UI-layer flaws (like protocol handlers, file-picker interactions, or IPC message deserialization) to break out of the sandbox and gain full control of the machine. The UI layer and its communications with content are critical attack surfaces, which is why keeping that code aligned with upstream security hardening is essential.

[dftf]

That reply just feels like a copied-and-pasted AI chatbot response? 😐

Anyway, the main point is: a fork of Firefox that chooses to stick with Proton doesn't automatically become insecure; that's only if they don't maintain it.  Obviously people need to look into forks and research whether they are regularly-updated (which in many cases is a simple as: look at the "releases" page on their GitHub).

But long-term, people who dislike Nova are going to have an issue, as the current 153 ESR will only last a year.  Assuming Mozilla don't reverse-course given the recent feedback on here over it, that leaves two choices: accept Nova when the time comes, or find a fork of Firefox which offers a UI they'd prefer.

[JNavas]

> That reply just feels like a copied-and-pasted AI chatbot response? 😐

My reply was drafted by me based on my professional software engineering experience with only a critique by AI for accuracy and completeness.

> Anyway, the main point is: a fork of Firefox that chooses to stick with Proton doesn't automatically become insecure; that's only if they don't maintain it.

Read my reply more carefully: "When a fork freezes a legacy UI while upstream keeps moving, backporting fixes becomes exponentially harder." [emphasis added] Worse, there's no way for a typical user to accurately judge the updating methodology of a fork.

In the long term, I think the more viable choice if Mozilla does not fix the Nova mess is to switch to a fully supported and maintained browser, like Microsoft Edge, in this new age of AI attacks.

[dftf]

Move to... Microsoft Edge? 🤔

Um, sure, I guess that's an option... but bit extreme.  That's like saying "I don't like this new UI update Sony have just done on PS5, so I'm going to get a Series X" or "I dislike Windows 11, I'm going to move to a Mac".  Okay, but then you've got an entirely new UI to deal-with, different settings screens, and you'll have to setup all extensions again (that's assuming they're all available: virtually all should be, but Manifest v2 ones, like the full uBlock Origin, are now only in Firefox -- though Brave have chosen to still support the v2 versions of AdGuard, NoScript, uBlock Origin and uMatrix, but that's it. v3 for the rest).

I mean, if someone is using a regular edition of Windows 11 or 10 then Edge is right-there, preinstalled.  The fact they post on this forum suggests they prefer Firefox, otherwise they'd just be using Edge now.

Though not sure why that is the only choice for a "fully supported and maintained browser" after the 153 ESR ends... Google Chrome pushes updates before Edge, and Brave usually within 1-2 days tops too.  Opera and Vivaldi often aren't far-behind either. (And there's always Safari for macOS users, of course).

Not sure Edge is the only choice?

[cadwellm]

That's why I went to Waterfox. Set it up using my Firefox profile so it is exactly the same as my Firefox was before the abysmal update they call 'Nova'.

It's Nova alright...made my brain explode as soon as I saw the changes.

[KrownProductsLt]

Sound is borked in 157 for Linux Mint. Volume levels are too low on all videos. Had to install 'Sound Adjuster' plug-in and set db gain to 3x to get audio levels restored. Not an issue with Vol Control, headsets, muting, external speakers, recent Linux updates or anything else hardware related. This is only happening with Firefox 157.0.1 from the pushed update. Reviewed the audio settings in About:config but could locate an issue.

Please fix this problem.

[JNavas]

The best solution to the ugly, less functional Nova UI (at least for the next year) is to switch from regular Firefox to Firefox ESR (Extended Support Release), which retains the classic Proton UI and is also more stable. See Navas' Tips: Firefox UI Debacle

[sosasees]

 With how Mozilla is clearly disreguarding User Feedback now, we need Helium and Ladybird to save our Web Browsing Experience.

[dftf]

Yeah, might be waiting a while for Ladybird... all you can do for now is download the source-code and build yourself (and then, only on macOS or Linux) to get a window with a URL bar but nothing else.

Windows will come years later, followed-by Android and iOS much-later.  So for now, you might be better-off looking into a "fork" of Firefox (e.g. Basilisk • Floorp • Librewolf • Pale Moon • Waterfox), or look into the business version which predates the new UI.  Details here:
https://tips.navas.us/2026/10/firefox-ui-debacle.html 

[JNavas]

Version 153.5.0, first offered to ESR channel users on October 13, 2026
I confirm this update retains the classic Proton UI. 👍👍

[noonespecial1]

change it back

[leojth]

Mozilla, if you think "they will get used to it", I can tell you that I never liked or got used to the detached tab buttons, but I could tolerate it. This new design, I can not tolerate.

When new design comes, I usually try to use it for a while, but this I had to revert immediately. Active "tab" looks like a text box, not a tab. (if it actually was a text box it would be rather cool). Together with adress bar it looks like two misaligned text boxes (dark mode, horizontal tabs).

My opinion is that at least the active tab should look like a tab and not something else.

[Makoto]

There seem to be many critical voices, but I personally think the new design is better than the previous one.
However, the tab design for "Container Tabs" doesn't appear to have been updated to match the new look, so I would like to see that addressed.

[dftf]

> "... I personally think the new design is better than the previous one"

You appear to use macOS, so obviously the new design fits in the best on that system.

It looks odd though on Windows and most Linux distros that don't try to mimic the macOS look (e.g. elementaryOS).  So glad you like, and enjoy, but they should allow others to reverse the look easily.

[nordo]

This new theme/look is horrible. I can't stand how it looks. Stop forcing this garbage on us.

[dftf]

You can consider move to 'ESR' version to avoid new look for about a year from now, see:
https://tips.navas.us/2026/10/firefox-ui-debacle.html 

[MrMoosticles]

If want useless bells and whistles i will use Opera. I use firefox because of its ease of use and extensive extension library. You are going down a **bleep** path with last few updates. We want simplicity, efficiency and reliability not deep umber or profiles.

[sosasees]

I very much dislike the Nova Style.
It looks great in Landmarks like the Firefox Website and About Window
but it’s super distracting in the actual Browser.

To fix the big Issues that i have with Nova, i changed advanced Firefox Settings like this:

1. Download the Proton Theme to grey out the garish Colors that clash with most Websites.
   Unfortunately, this does not reduce how much the Corners are rounded, even though the Preview Image suggests that.
2. Enable the Secret Setting that lets you change the Browser’s Look with CSS Styles.
   In about:config, this Setting should be toggled on (true):
   toolkit.legacyUserProfileCustomizations.stylesheets
3. Open the Page about:support to find Profile Directory and open it.
4. In that Profile Directory, create the Folder chrome, if it isn’t already there.
5. In the chrome Folder, create the File userChrome.css and edit it.

My userChrome.css File looks like this:
Though yours may look different, based on your Priorities and Firefox Version.
This Stylesheet is for Firefox Version 160.

/* START Nova Rounding Adjustments */
:root {
    --border-radius-xsmall: 2px !important; /* Nova Default: 4px, Proton Default: 2px */
    --border-radius-small: 4px !important; /* Nova Default: 8px, Proton Default: 4px */
    --border-radius-medium: 6px !important; /* Nova Default: 12px, Proton Default: 8px */
    --border-radius-large: 8px !important; /* Proton Default: 16px, [Undefined in Nova] */
    --border-radius-xlarge: 10px !important; /* Nova Default: 24px, [Undefined in Proton] */

    
    --tab-border-radius: var(--border-radius-medium) !important;
    
    --button-border-radius: var(--border-radius-small) !important;
    --toolbarbutton-border-radius: var(--border-radius-small) !important;

    /*--card-border-radius: var(--border-radius-small) !important;
    --card-border-radius-compact: var(--border-radius-small) !important;
    --card-cover-image-border-radius: var(--border-radius-small) !important;

    --input-text-border-radius: var(--border-radius-small) !important;

    --menuitem-border-radius: var(--border-radius-small) !important;

    --popup-border-radius: var(--border-radius-small) !important;*/

    --panel-border-radius: var(--border-radius-large) !important;
    --panel-menuitem-border-radius: var(--border-radius-medium) !important;
    
}
.tab-group-label, .tab-group-label-hover-highlight {
    border-radius: var(--border-radius-medium) !important;
}
tabpanels, .browserContainer  {
    border-radius: 0 !important;
}
.urlbar-background, .urlbar-input-container {
    border-radius: var(--border-radius-small) !important;
}
sidebar-bookmark-row, details summary, sidebar-tab-row, input {
    border-radius: var(--border-radius-small) !important;
}
/* END Nova Rounding Adjustments */

I started with this Stylesheet and modified it with Help of Browser Toolbox to address remaining Spots which look wayy too rounded.
I especially hate the Droplet Shape of the Tab Group Headings, so this Stylesheet also turns them back into Rectangles.
I also dislike how the Web View is rounded at only the top left Corner when i enable vertical Tabs, so this Stylesheet sharpens the only rounded Corner of the Web View.

---

UserChrome.css only changes the Browser Chrome. It cannot touch the Browser UI inside the Web View.
To style Firefox Pages like New Tab and Settings and Firefox View, you need another Stylesheet named UserContent.css, in the same chrome Folder.

I did not setup a UserContent.css File because i find Nova’s subpar Design not so distracting on Pages that i don’t see that often when browsing
but i know that many Users can’t stand the round Edges and purple Highlights even on the Settings Page.

---

I did not use GenAI when making this Stylesheet.
This was a 4‑Hours‑long Project with proper Quality Control.

---

If Firefox Staff reads this, they may notice the Result is very similar to the actual Proton Design of Firefox up to Version 156.
A Less rounded Corners Setting should be built into Firefox, so that Step 2 and beyond don’t need to be done.
By reverting the epic Fails of Nova, these Improvements shine:

• Tab Groups no longer change Color when opened or closed.
• Compact Mode is now more compact.

[JNavas]

Firefox ESR is a better solution. See Navas' Tips: Firefox UI Debacle 

[Agentvirtuel]

Bonjour

I'm not a fan the Nova Style.

I use css, https://connect.mozilla.org/t5/discussions/the-new-firefox-design-lands-in-today-this-is-what-you-ca...