Tacet
Free, open-source native Mac browser on WebKit: Arc-style sidebar, Spaces, Arc import and built-in blocking.
Tacet (formerly Lumen) is a free, GPL-3.0 macOS browser written in Swift and SwiftUI on the system WebKit engine, made by one developer and pitched at people leaving Arc. It has a vertical sidebar that hides with ⌘S, tab groups, pinned tabs that keep their site, Spaces that swap a window's whole tab set, a command bar, two-pane split view, link preview, per-site rules that send links to a Space or profile, and Customize Site for per-site CSS, JavaScript and hidden elements. It imports Arc's Spaces, Favorites, pinned tabs and folders, but as tab groups and pinned tabs, not as Spaces. Tacet Shield blocks ads and trackers by default, and an assistant runs on Apple's on-device model, Ollama or your own key. Extensions need macOS 15.4 and are added by hand. Passkeys do not work and there is no live sync or mobile app. Release builds are universal, need macOS 14 and are not notarized, so first launch needs one Terminal command.
60% Arc feature parity (yes = 1, partial = ½).
AI optional
Assistant panel (⇧⌘A) is off by default; turn it on in Settings › AI, then use your own key, Ollama/LM Studio or Apple's on-device model.
github.comNot counted in Arc parity: some people want AI, some avoid it.
None found
Guide: no accounts or analytics. Network use is update checks, filter lists, search suggestions and the AI provider you choose; no ads, wallet, feed or upsell found.
github.comAds, crypto, paid upsells, news feeds, default-on telemetry, required accounts.
Organization
| Feature | Tacet | Arc | Note |
|---|---|---|---|
| Vertical sidebarTabs live in a vertical sidebar that is the main tab UI and can be hidden. | ✓ | ✓ | Vertical sidebar is the default layout (top bar optional); ⌘S hides it and hovering the edge peeks it.github.com |
| SpacesSeveral workspaces per window, each with its own pinned and open tabs, switched by swipe or shortcut. | ✓ | ✓ | Spaces swap every tab, pinned tab, group and split in the window; sidebar icons or ⌃⌘←/→ switch.github.com |
| Profiles per Space (shareable)Each Space can use its own browser profile (separate cookies, logins, history), and one profile can be shared by several Spaces. | ◐ | ✓ | A Space belongs to its window's profile (own logins); no switching to another profile's Space in-window.github.com |
| Global favoritesPinned icons at the top of the sidebar shared by every Space (Zen calls them Essentials). | ◐ | ✓ | Pinned tabs show as icons at the top but live inside each Space; nothing is shared across Spaces.github.com |
| Pinned tabs & foldersPer-space pinned tabs that act like bookmarks, with nested folders. | ◐ | ✓ | Per-Space pinned tabs; groups are separate, pinned tabs can't join a group and groups don't nest.github.com |
| Auto-archive tabsUnpinned tabs close automatically after a set time and stay recoverable in an archive. | ◐ | ✓ | Unpinned tabs close after a day, week or month (off by default); no archive view.github.com |
| Space themesPer-space colour or gradient themes. | ◐ | ✓ | Each Space picks an accent colour and icon for its sidebar header; no per-Space theme or gradient.github.com |
Browsing
| Feature | Tacet | Arc | Note |
|---|---|---|---|
| Split ViewTwo or more tabs side by side in one window. | ◐ | ✓ | Split view shows two pages side by side (⌥⌘S); no third or fourth pane.github.com |
| Link previewOpen a link in an overlay without leaving the current page (Zen calls it Glance). | ✓ | ✓ | ⌥-click or right-click a link opens it in a panel over the page; Esc closes, ⌘↩ keeps it as a tab.github.com |
| Mini windowA small, chrome-less window for links opened from other apps or a quick search. | ✕ | ✓ | Arc's Little Arc has nothing like it in Tacet, per its own Arc comparison table.github.com |
| Command barA ⌘T palette that searches tabs, history, bookmarks and browser commands. | ✓ | ✓ | ⌘L/⌘K bar searches open tabs, bookmarks, history and commands; also does sums and unit conversions.github.com |
| Link routingRules that send links from other apps to a chosen space or profile. | ✓ | ✓ | Settings › Opening rules: per-site rules send links from other apps to a Space, profile or private window.github.com |
| Site customizationPer-site custom CSS/JS, or zapping elements off a page. | ✓ | ✓ | Customize Site: per-site theme and font, pick elements to hide, your own CSS and JavaScript.github.com |
| Auto picture-in-picturePlaying video pops out into picture-in-picture automatically when you switch tabs. | ◐ | ✓ | Picture in Picture is a bundled plugin you trigger by hand with ⌥⇧P; nothing pops out on tab switch.github.com |
Compatibility & migration
| Feature | Tacet | Arc | Note |
|---|---|---|---|
| Arc importImports Arc spaces, pinned tabs and folders. | ✓ | – | Reads Arc's StorableSidebar.json: Spaces and folders become tab groups, Favorites pinned tabs.github.com |
| Chrome extensionsInstalls extensions from the Chrome Web Store. | ◐ | ✓ | No Chrome Web Store installer; add an unpacked folder, .zip or .crx by hand (macOS 15.4+ only).github.com |
| DRM (Widevine)Netflix, Disney+, Spotify web and other DRM video/audio play. Chromium forks need a Google Widevine licence. | ? | ✓ | |
| PasskeysWebAuthn passkeys, Touch ID and the system/iCloud keychain. | ✕ | ✓ | WebKit refuses passkeys without Apple's browser entitlement; Tacet offers Sign In with Safari instead.github.com |
| SyncSpaces, pinned tabs and settings sync across devices. | ◐ | ✓ | No live sync; an encrypted backup file moves Spaces, tabs, history and passwords by hand.github.com |
| Mobile appiPhone, iPad or Android app that shares spaces with desktop. | ✕ | ◐ | Mac only: requirements list macOS 14+ and releases ship only a macOS DMG.github.com |
Extras
| Feature | Tacet | Arc | Note |
|---|---|---|---|
| Built-in ad blockerAd and tracker blocking without installing an extension. | ✓ | ✓ | Tacet Shield blocks ads and trackers with WebKit rules, on by default, plus cookie banners and YouTube ads.github.com |
Extension support
Which extension formats and stores run, beyond the Chrome Web Store row above. Not counted in Arc parity.
| Feature | Tacet | Arc | Note |
|---|---|---|---|
| Manifest V2 extensionsThe older extension format Chrome removed in 2025. Needed for full uBlock Origin and other extensions that block requests. | ◐ | ✕ | WebKit loads MV2 but webRequest can't block, so no full uBlock Origin; Tacet adds no patch.github.com |
| Manifest V3 extensionsThe current extension format used by the Chrome Web Store (and supported by Firefox and Safari). | ✓ | ✓ | MV3 extensions load through WebKit's WKWebExtension on macOS 15.4+; not tested one by one.github.com |
| Firefox add-onsAdd-ons from addons.mozilla.org or .xpi files install and run. | ◐ | ✕ | Only manual .xpi installs; no addons.mozilla.org installer, and Firefox-only APIs won't work.github.com |
| Safari extensionsSafari web extensions (the App Store extension apps Safari uses) install and run. | ✓ | ✕ | Safari web extensions inside apps in /Applications are listed and added with one click.github.com |