Zen Browser vs Firefox for Arc Users in 2026

By Kshetez Vinayak, founder of SupaSidebar. Last updated November 13, 2026.

TL;DR

In Zen browser vs Firefox, Zen is the closer copy of Arc and Firefox is the safer browser to keep. Zen is a free, open-source browser built on Firefox's code that rebuilds Arc's sidebar with Spaces, Essentials and, since October 29, 2026, an Arc importer. Plain Firefox has vertical tabs, tab groups and Split View but no Spaces, and unlike Zen it plays Netflix and Spotify on a Mac and gets Mozilla's security fixes first. Pick Zen for Spaces inside the browser, or pick Firefox and add SupaSidebar to put Arc's sidebar, Spaces and pinned tabs on top of it. A feature map, the one published Mac speed test and a count of Zen's update lag are below.

Quick navigation

• Only weighing Zen against Arc itself? → Zen vs Arc Browser
• Already picked Zen and need your Arc Spaces in it? → How to Move From Arc to Zen
• Comparing Zen with Helium instead? → Helium vs Zen Browser for Arc Users
• Weighing Firefox against Safari? → Firefox vs Safari on Mac
• Want to see which browsers keep each Arc habit? → Which Browsers Have Arc's Features
• Choosing between Zen and plain Firefox after Arc? You are in the right place. Keep reading.

Zen vs Firefox at a glance

Why Arc users are choosing between Zen and Firefox now

Arc for macOS and Windows stops working on December 22, 2026, and every Arc account is deactivated the same day, according to the Arc farewell page. For Arc users who want to leave Chromium, the shortlist usually comes down to two browsers with the same engine and very different interfaces.

Zen is Firefox underneath. Zen's own FAQ says its codebase is derived from Firefox, and each Zen release names the Firefox version it is built on, such as Zen 1.24.1b on Firefox 159.0.1 on November 6, 2026. The difference is the layer on top, where Zen rebuilds Arc's sidebar and plain Firefox keeps a more traditional window.

Reddit users frame it the same way. In a count of the 10 top replies to the r/browsers thread "Firefox vs Zen", posted October 22, 2026 by an Arc user and read on November 10, 4 replies leaned toward Zen for its Arc-like layout, 2 picked plain Firefox, 2 suggested a different browser and 2 made no pick. Three of the 10 said outright that Zen is Firefox with a different interface, and a fourth noted that Zen depends on a smaller team to pass on Firefox's security fixes. One Firefox pick cited Mozilla's larger professional team, and the other said Firefox can be set up to look much the same. It is a small, single-thread sample, so read it as the shape of the debate rather than a vote.

Where Arc's features land in Zen and in Firefox

Zen keeps far more of Arc's model than plain Firefox does, but Firefox has added most of Arc's layout pieces since 2025. This map shows where each Arc habit ends up, with what SupaSidebar adds on top of plain Firefox.

The Spaces row is the whole Zen vs Firefox decision for most Arc users. Every other row has a Firefox answer, and Spaces does not.

Zen is closer to Arc because it has Spaces

Zen is the better pick for Arc users who organized their day around Spaces, because it is the only one of the two that has them. Zen's Spaces each hold their own pinned and open tabs inside one window, and each Space can get a default container that keeps one account's cookies apart from another's, per Zen's Spaces documentation. Since Zen 1.22b, Spaces, folders and tabs sync between devices through a Mozilla account.

Zen also closed the Arc import gap before the shutdown. Zen 1.24b, released October 29, 2026, can "import Spaces and Profiles from Arc and Dia", turning Arc's Spaces into Zen Spaces and its Favorites into Essentials. The importer reads Arc's data folder on the Mac, so Arc's files must still be there when it runs. The Arc to Zen guide walks through it.

Plain Firefox has caught up on layout but not on Spaces. Between March 2025 and March 2026 it added vertical tabs, tab groups, a profile switcher and Split View, and Firefox 157 turned the updated sidebar on for everyone on September 29, 2026, alongside what Mozilla calls its "biggest visual refresh in years".

What Firefox still lacks is a way to keep separate sets of tabs in one window. In a November 17, 2025 post, Mozilla listed workspaces as a request it was still weighing, a way "to separate contexts by creating workspaces". No Firefox release notes since then mention them. Firefox's tab groups also stay on one computer, since Mozilla's tab groups help page says they do not sync with Firefox Sync.

Zen browser vs Firefox performance, from measured tests

Zen and Firefox perform close to each other, since Zen runs Firefox's own engine, and the one published Mac benchmark of the two found Zen slightly slower. On a MacBook M3 Pro, Jitbit's browser benchmark scored Firefox 134.0.2 at 34.8 and Zen 1.7.3b at 31.6 on Speedometer 3.0, about 9% lower for Zen. Both versions date from early 2025, so treat the gap as directional.

Memory is harder to pin down, and no current, controlled test of Zen against Firefox memory use was found. Jitbit's author later wrote that the RAM comparison in that post counted only the main Firefox and Zen processes, leaving out helper processes that the post says "almost double the memory load", so its memory chart should not be quoted either.

At least some of Zen's memory fixes come straight from Mozilla. Zen 1.24b's notes list a fix for "memory usage growing rapidly when sites such as the Zoom web app were left open in a minimized window", the same line that appears in Firefox 159's release notes two days earlier. Reddit threads about Zen using more RAM than Firefox are common, but they are reports from single machines, not measurements.

For Zen browser memory usage vs Firefox, the practical read is that page rendering is the same code in both. Differences come from what Zen adds around the page, such as its sidebar, themes and Mods, and from how many tabs and extensions are open.

Netflix and Spotify play in Firefox, not in Zen on a Mac

Plain Firefox is the better pick for Arc users who stream in the browser, because Zen on a Mac cannot play DRM-protected video or music yet. Zen's FAQ says Zen "currently lacks DRM support" because it does not have a Widevine license, that this affects macOS and Windows, and that the team is waiting for approval from Google. The FAQ lists Netflix, HBO Max, Spotify, Disney+, Amazon Prime Video, Apple Music and Google Play Movies & TV as services that will not stream in Zen.

Zen's own FAQ points users to Firefox, or to a service's desktop app, for that content. One of the Zen recommenders in the r/browsers thread raised the same catch, saying Netflix or Spotify still need another browser. For an Arc user moving to Zen alone, that means keeping a second browser just for streaming.

Updates and staying power favor Firefox

Firefox is the safer long-term pick, because Mozilla ships its security fixes first and has maintained Firefox since version 1.0 on November 9, 2004, per Mozilla's own release history. Zen has to take each Firefox update, rebuild its own layer on top and release it, so Zen users always wait a little.

That wait is short but real. Matching Mozilla's release history against Zen's GitHub releases for every Firefox update from September 15 to November 3, 2026 shows Zen shipped each one 1 to 4 days later, 2 days on average across 8 updates.

Zen is an active project. It shipped 7 stable releases between October 3 and November 6, 2026, and its GitHub repository has more than 45,000 stars under the Mozilla Public License 2.0. Zen's about page lists Mauro V. as creator and main developer, with a group of contributors, and asks users for donations to fund development.

Mozilla's footing is different. In September 2025, a US court ruling in the Google search case rejected a proposed ban on search payments to small, independent browsers such as Firefox, as Mozilla wrote at the time. Mozilla said such a ban would have made it harder for independent browsers to compete, and Mozilla has now shipped Firefox for more than two decades.

Some Arc users are choosing on exactly this point. One r/ArcBrowser user explained their move back to Safari with SupaSidebar in one line, "Just don't want another browser which will disappear."

Extensions and sync work almost the same

Extensions are not a reason to choose between Zen and Firefox, because both install the same add-ons from Mozilla's store, and Zen's FAQ says it integrates with Firefox Sync for add-ons, bookmarks, history and passwords. The difference is that Zen also syncs its Spaces between computers, while Firefox's tab groups stay on one. Zen is desktop-only, offered for macOS, Windows and Linux on its download page, so on a phone the same Mozilla account goes into Firefox either way.

The gap neither browser closes

Zen and Firefox both assume an Arc user will live in one browser. Plenty never did. Chrome often stays open for a work account, Safari for battery life, and Zen users still need a second browser for Netflix and Spotify.

Zen's Spaces only exist inside Zen, and Firefox has no Spaces at all. A sidebar locked inside one browser has to be rebuilt every time that browser changes, and Arc's shutdown just showed how fast that can happen. The question for a stability-first Arc user is how to get Spaces without betting on a smaller browser.

SupaSidebar brings Arc's sidebar and Spaces to plain Firefox

SupaSidebar adds Arc's sidebar, Spaces and pinned tabs to plain Firefox as a native Mac app that sits outside the browser, so Arc users can keep Mozilla's stable browser and still work in Spaces. SupaSidebar is not a browser and not a browser extension. It works next to Firefox and 32+ other supported browsers, and it runs on macOS 14 and later.

SupaSidebar's Live Tabs section shows Firefox's open tabs in the sidebar, and clicking one switches to that tab instead of opening a duplicate, per the Live Tabs docs. Since SupaSidebar 1.6.0, a Space can be linked to Firefox, so that Space's links open in Firefox and its Live Tabs show only Firefox's tabs.

Three Arc habits come back on Firefox. A saved link lights up while it is your current Firefox tab, like a pinned tab in Arc, since SupaSidebar 1.4.0. Pressing ⌘T in Firefox opens SupaSidebar's Command Panel, like Arc's command bar, once browser keys are turned on. And Arc's Spaces, folders and pinned tabs come in through Preferences → Data → Import → Arc, with a preview first, as the Arc import guide shows. Choose File… also accepts a saved copy of Arc's StorableSidebar.json, so a backup still imports after December 22.

Here is a typical setup for an Arc user who moved to Firefox and still keeps Chrome for one client.

Switching Spaces swaps the whole sidebar with one shortcut, and each Space opens links in its own browser. If Firefox is ever replaced, the Space is relinked and nothing is rebuilt. In a review on r/macapps, one user wrote that SupaSidebar "recreates much of that [Arc] experience, but does it across multiple browsers instead of inside just one."

SupaSidebar has limits worth knowing. A Space links to Firefox as a whole browser, not to a single Firefox profile, and SupaSidebar Spaces do not isolate cookies, so Firefox profiles remain the way to keep two Google accounts apart. SupaSidebar also does not change Firefox's own tab strip or move passwords, history and extensions, which stay in Firefox.

Which should you pick, Zen or Firefox?

• If Spaces inside the browser were the reason you used Arc, pick Zen. It has Spaces, Essentials and an Arc importer, and its Spaces sync between Macs.
• If you stream Netflix, Spotify or Disney+ in the browser, pick Firefox. Zen on a Mac cannot play DRM content until it gets a Widevine license.
• If you want security fixes on day one and a big organization behind the browser, pick Firefox. Zen ships each Firefox update 1 to 4 days later.
• If you want Arc's Spaces and Mozilla's stability together, pick Firefox and add SupaSidebar for Spaces, pinned tabs and Arc import.
• If you are not sure yet, export Arc's sidebar first, as the Arc sidebar export guide explains, so nothing is lost while you try both.

What Arc users should pick before December 22

Zen is the closer Arc replacement and Firefox is the more stable browser. Zen keeps Arc's Spaces, pinned tabs and Essentials, imports Arc since October 29, 2026, and syncs Spaces between Macs. Firefox plays DRM content on a Mac, gets Mozilla's security fixes 1 to 4 days before Zen, and has Mozilla behind it.

Spaces-first Arc users who rarely stream in the browser should choose Zen and run its Arc import before December 22. Arc users who stream in the browser, or who do not want to bet on a small team, should choose plain Firefox. Arc users who want both, Mozilla's Firefox and Arc's Spaces, should keep Firefox and put Arc's sidebar on top with SupaSidebar, which imports Arc's Spaces and shows Firefox's open tabs live.

Whichever way you go, save Arc's sidebar before December 22. To keep Arc's Spaces on plain Firefox, try SupaSidebar (free version available).

Why we recommend SupaSidebar

SupaSidebar is a macOS app that brings Arc's sidebar to every browser - one sidebar for tabs, bookmarks, files, and apps across 32+ browsers including Safari, Chrome, Firefox, Edge, Brave, Vivaldi, Helium, Dia and Orion. For Firefox it shows open tabs in Live Tabs, links Spaces to Firefox, opens its Command Panel on ⌘T, and imports Arc's sidebar with a preview first. 3,000+ Mac users have tried SupaSidebar.

FAQ

Is Zen better than Firefox?

Zen is better than Firefox for Arc users who want Spaces, because Zen has Arc-style Spaces, Essentials and an Arc importer and plain Firefox has none of them. Firefox is better for streaming and stability, since it plays Netflix and Spotify on a Mac and gets Mozilla's security fixes 1 to 4 days before Zen. Firefox plus SupaSidebar adds Arc's Spaces to plain Firefox.

Is Zen browser faster than Firefox?

No, Zen is not faster than Firefox in the one published Mac test. On a MacBook M3 Pro, Jitbit's benchmark scored Firefox 134.0.2 at 34.8 and Zen 1.7.3b at 31.6 on Speedometer 3.0, about 9% lower for Zen. Both browsers use the same Firefox engine, so day-to-day page speed is close.

Does Zen use more memory than Firefox?

No current, controlled benchmark shows how much memory Zen uses compared with Firefox. Zen runs Firefox's engine and inherits Mozilla's memory fixes, such as the Zoom web app fix in Firefox 159 that Zen shipped in 1.24b. Reddit reports of higher RAM use in Zen exist, but they come from single machines, not measurements.

Can Zen play Netflix and Spotify on a Mac?

No. Zen's FAQ says Zen lacks DRM support on macOS and Windows because it does not yet have a Widevine license, and lists Netflix, Spotify, Disney+, HBO Max, Amazon Prime Video and Apple Music as services that will not stream. Zen's FAQ suggests Firefox or the service's desktop app for that content.

Is Zen just Firefox with a different look?

Mostly, yes. Zen's codebase is derived from Firefox, each Zen release is built on a named Firefox version, and Zen installs the same Firefox add-ons. Zen adds an Arc-style interface with Spaces, Essentials and Mods, on its own release schedule.

Does Firefox have Spaces like Arc and Zen?

No. As of November 2026, Firefox has vertical tabs, tab groups, profiles and Split View, but no Spaces or workspaces, and Mozilla described workspaces as an open request in November 2025. SupaSidebar adds Spaces on top of Firefox, with Firefox's open tabs shown in its Live Tabs section.

Does Zen sync with Firefox on my phone?

Partly. Zen integrates with Firefox Sync, so bookmarks, history, passwords and add-ons can follow one Mozilla account to Firefox on iOS or Android. Zen has no mobile app, and its Spaces sync only between Zen installs on desktop.

By Kshetez Vinayak, founder of SupaSidebar. Last updated November 13, 2026.