What Nova changed, and what Mozilla says
Firefox 157 was scheduled for September 29, 2026, as the release that makes Nova the default desktop interface. Mozilla's Add-ons blog called it the biggest interface refresh since Proton in 2021. According to that post, the browser frame is cleaner, the sidebar plays a bigger role, and vertical tabs are a first-class layout.
For theme authors, Mozilla documented several concrete changes:
- The toolbar and sidebar now sit flush with the window edges.
- The selected tab no longer has the shadow Proton drew under it.
- Non-default themes use the operating system's accent color for controls, but the default theme uses a purple accent.
- Mozilla is featuring a Proton theme in the Add-ons Manager for users who want the previous look.
The author's own complaint was narrower and personal. He says the interface got more padding and rounder, "floatier" elements. He also says his Container color markers turned into a thin, washed-out line. Containers separate logins, and he relies on the colors to tell them apart at a glance. This is a first-person account. I found nothing that confirms it for all users. Mozilla's blog comments do include a few readers with similar gripes, such as harsh container stripes on vertical tabs and trouble finding color-coded tabs.
The built-in escape hatch
There is no Settings toggle for Nova. The author searched Settings and found only a color scheme and a link to themes. The off switch is a hidden preference. Several independent guides describe the same steps:
- Type
about:configin the address bar and press Enter. - Click "Accept the Risk and Continue" if Firefox shows the warning page.
- Search for
browser.nova.enabled. - Set it to false. Restart Firefox if the old interface doesn't appear immediately.
Reports differ on whether a restart is needed. Korben says the old interface comes back with no restart needed, while other guides suggest restarting if anything looks off. To go back, set the value to true.
Caveats on the flag
- It is not an official setting. Mozilla doesn't list it in Settings, and it could stop working or be removed in a future Firefox version.
- Mozilla Support moderators have reportedly warned that the preference is expected to be removed. Windows Digitals, a how-to site, says it tested the switch on Firefox 157 and the interface reverted straight away.
- Sigma Browser, a rival browser vendor, says a Firefox engineer proposed removing the pre-Nova code starting with Firefox 161, which ships on November 24, 2026. Treat that as a proposal reported by an interested party, not a Mozilla commitment.
- Users on Mozilla Connect reportedly say menus stayed spread out even with Nova off. That is a secondhand report.
- Mozilla's blog commenters also say the accent color stays purple on Windows 10 and 11 even with other themes. This is user reporting, not confirmed behavior.
The old look is probably not a permanent option, so plan for that. The Firefox ESR line is another route for people who want the pre-Nova design. Sigma's comparison lists ESR 153 as keeping the whole pre-Nova design until September 2027. I haven't verified that date against Mozilla's release schedule, so check it before relying on it.
Why the author chose Floorp
Floorp is a Firefox fork, so Firefox add-ons carry over. The author installed version 12.20.2. Floorp's own release notes for 12.19.0, dated September 30, 2026, say it moved its base from Firefox 156.0.1 to 157.0. They also say Floorp disables Firefox 157's new Nova interface. That quote isn't from the page I'm citing here, so treat the exact wording as paraphrase. The notes say the team adjusted compatibility for sessions, Split View, colors and private containers.
Those notes also carry a warning that matters for anyone who might follow him. Floorp says it doesn't know how long Mozilla will keep the previous interface available. They add that some design options may become temporarily unavailable or display inconsistently. So Floorp's old-style look depends on code Mozilla controls, just like the about:config flag does.
What he found in Floorp
His account of the tested build, which I couldn't confirm in official sources, is as follows:
- Interface designs: He opened the hamburger menu, then Floorp Hub, then Tab & Appearance. There he found five designs: Proton, Lepton, Firefox UI Fix, Photon and Fluerial. Lepton is the default, and he says it looked a lot like Edge. He picked Firefox UI Fix, and his container colors were bold again.
- Workspaces: Each workspace can have its own container, so tab color shows which workspace you're in. He runs about five, including Inbox, Research Hub and School.
- Sidebery: He says it works on Floorp but he didn't install it. He misses its tab tree.
- Split view: He says Floorp allows four pages side by side, which he used for Android battery research.
Floorp's official notes support part of this. In 12.19.0 it moved 25 interface options previously tied to Lepton-based designs into shared Chrome Extras settings. That makes them usable with designs like Proton and Fluerial. Floorp's 12.12.0 notes describe Split View with up to four panes and a choice of vertical, horizontal or grid layouts. Firefox's own Split View, introduced in Firefox 149, supports only two tabs, according to the author's reading of Mozilla's support page.
The cost: stability and version drift
The author is candid about Floorp's downsides. It froze a few times with a "not responding" message when he loaded many tabs across workspaces, and some tabs opened slowly. Floorp's blog lists a 12.20.1 release on October 9 that addressed rapid memory growth and freezes under certain conditions. That doesn't prove he hit the same bug, and he was on 12.20.2, which came later.
His version is also already behind. Floorp's blog lists 12.21.1 as the latest release, dated November 4. It updates the Firefox base to 159.0.1 and includes a fix for CVE-2026-120572, a page-layout vulnerability Mozilla rates High. That does not mean his build was vulnerable. It does show that a fork must track Mozilla's security releases. You are trusting a small team to keep pace.
Which route fits you?
| Goal | Option | Trade-off |
|---|---|---|
| Just the old look | Set browser.nova.enabled to false | Unofficial, may be removed |
| Official, lower-risk look change | Mozilla's Proton theme | Reportedly doesn't fully restore the old look |
| Stability and the pre-Nova design | Firefox ESR | Ends up on an older feature set |
| Looks plus workspaces and four-way split | Floorp | Third-party fork, stability caveats |
Bottom line
Nova is a reminder that browser interface changes are often reversible only through hidden switches with an expiry date. If you only dislike the look, the about:config flag is the cheapest fix. Use it knowing it may vanish. Floorp is worth trying if you also want its extra features, and the author's experience says it is more than a reskin. Keep it updated, because it follows Mozilla's releases and security fixes. This article reports one writer's experience on one set of versions. Menus, options and behavior may differ on the current Floorp release.