Zen Browser 1.24b ships an Arc migration path, shareable Boosts, and Firefox 159
The Firefox fork adds a way to import Spaces and Profiles from the dying Arc, rounds out its per-site Boosts, and pulls in the Firefox 159 engine.
Zen Browser is quietly becoming the browser Arc's designers never had to worry about competing with, and now it's going after Arc's users directly.
The open-source Gecko fork shipped Zen 1.24b on October 29, and the update includes a migration path aimed squarely at people displaced by the impending shutdown of Arc. It also finalizes its "Boosts" per-site customization tool and brings the whole thing up to Firefox 159.
Arc's going away. Zen is ready.
Arc, the browser that shaped Zen's entire "calm interface" aesthetic, is winding down. The Browser Company stopped active development back in May 2025, was reportedly sold to Atlassian that September, and now has Arc scheduled to go dark on December 22, 2026. Users are being steered toward Dia, an AI-focused successor.
Zen 1.24b lets you import both Arc "Spaces" and your profiles straight in. On top of that, it reads Dia too, so the door stays open even after the switch. Not bad positioning for a project built as an homage.
It helps that Zen has become Arc's spiritual successor in practice: vertical tabs, workspaces, split view, and Glance link previews all come from that Arc playbook, wrapped around Firefox's Gecko rather than Chromium.
Boosts, Firefox 159, and the rest
Boosts are Zen's per-site tweak tool. They landed in 1.20, letting you tint colors, retouch fonts and styling, zap page elements, and force dark mode on any site. In 1.24b they can finally be shared with other people, plus a general quality bump. The payoff is that your favorite site tweaks become portable instead of trapped on a single machine.
There's also a "Paste & Search" action: hold Ctrl while hovering the new-tab button, and you can drop in a URL or snippet and search at once. You can now add or remove tabs directly from the Library, and a new indicator flags tabs whose content isn't currently visible.
Under the hood this is still Firefox, Zen 1.24b runs on the 159.0 engine. That matters for one recurring selling point: because Zen sidesteps Google's Chromium and its Manifest v3 limits, ad blockers like uBlock Origin work unrestricted. It's arguably the single most durable advantage Zen holds over Chromium competitors, and reviewers keep circling back to it.
Security and the fine print
As a fork, Zen inherits Mozilla's security updates, and this release explicitly folds in advisory MFSA2026-118. The fix list covers a long tail of platform-specific annoyances: memory ballooning when you leave the Zoom web app open and minimized, videos misrendering with NVIDIA RTX Video HDR on Windows, and tabs sometimes detaching into new windows on Linux Wayland. They now also display non-Latin URLs, Javanese, Balinese, and friends, in their native script instead of raw punycode.
Head here to the full release notes if you want every nitty-gritty detail.
