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.
Built-in AI
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.comBloat check
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 |
|---|---|---|---|
| SidebarVertical 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 |
| ProfilesProfiles 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 |
| FavoritesGlobal 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 TabsPinned 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 |
| Live foldersSidebar folders that fill and refresh themselves from an outside source, such as GitHub pull requests or an RSS feed. | ✕ | ✓ | No live-folder code at 0df72d2; tab groups are plain user or per-site groups with no feed or refresh source.github.com |
| ArchiveAuto-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 |
| Theme pickerSpace 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 |
| PeekLink 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 |
| Little ArcMini 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 |
| Air Traffic ControlLink 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 |
| BoostsSite 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 PiPAuto picture-in-picturePlaying video pops out into picture-in-picture automatically when you switch tabs. | ◐ | ✓ | Picture in Picture is a store plugin you trigger by hand with ⌥⇧P; nothing pops out on tab switch.github.com |
| Mini playerMedia still playing in a tab you left keeps play/pause controls in the sidebar. | ◐ | ✓ | A speaker icon on playing tabs in the sidebar only mutes; there is no play/pause or now-playing control.github.com |
| Tab SwitcherRecent-tab switcherCtrl+Tab jumps back to the tab you used last and cycles in recently used order. | ◐ | ✓ | ⌃Tab steps in tab-strip order; only the command bar at rest lists the six most recently used tabs.github.com |
| Super CopyClean link copyA shortcut (⌘⇧C) copies the page URL with tracking parameters removed. | ◐ | ✓ | ⇧⌘C copies the link unchanged; Copy Link Without Tracking (utm_, fbclid…) sits in the ⋯ menu and command bar, no shortcut.github.com |
| CaptureScreenshotsBuilt-in capture of a chosen area or element, and of the full page. | ✓ | ✓ | File menu: screenshot of the visible page (⇧⌘S), whole page (⌥⇧⌘S) and a picked element; each is copied and saved as PNG.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 streamingNetflix, Disney+, Spotify web and other DRM video/audio play, through Widevine or, on WebKit, FairPlay. Chromium forks need a Google Widevine licence; FairPlay counts once a major service is confirmed playing in the app. | ? | ✓ | |
| 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 |
| Custom ShortcutsShortcut editorMost browser keyboard shortcuts can be remapped in Settings. | ✕ | ✓ | Help > Keyboard Shortcuts is a read-only list; only automations can take ⌃⌥⌘1–9 keys.github.com |
More Arc features
Arc features shown but not counted in the score, because almost no replacement has them or only a few people need them.
| Feature | Tacet | Arc | Note |
|---|---|---|---|
| EaselsA shareable canvas of live page captures, notes and drawings. | ✕ | ◐ | No canvas or board code at 0df72d2; the Library only lists history, bookmarks, reading list, highlights and downloads.github.com |
| Shared CollectionsShared spaces & foldersShare a Space, folder or set of tabs as a link anyone can open, or another user can add to their sidebar. | ✕ | ✓ | Only a whole-bookmarks HTML export; no way to share or export a space, folder or set of tabs.github.com |
| PreviewsWeb app previewsHover a pinned Gmail, Calendar or other web app to glance at it; a pinned calendar shows the next meeting with Join. | ✕ | ✓ | Hovering a tab shows a page thumbnail and memory use only; no live web-app glance or unread badges.github.com |
| Developer modeA developer view that turns on by itself for localhost: full URL, quick DevTools and dev tools in reach. | ◐ | ✓ | Settings > Advanced > Developer Mode (manual, global) adds a Develop menu: inspector, page source, page info, responsive mode, user agents.github.com |
Extension support
Which extension formats and stores run, beyond the Chrome Web Store row above.
| 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 |