Circa
Free, open-source native Mac browser on Chromium with Spaces, Peek, Little Circa, Boosts and an ad blocker.
Circa is a free, MIT-licensed Mac browser with a Swift and AppKit interface on a patched Chromium 158 (CEF) engine. It pitches itself at Arc users: a sidebar, Spaces tied to profiles, pinned tabs and folders, auto-archive, a Command Bar, up to four-way Split View, Peek, Little Circa, per-site CSS/JavaScript Boosts, Air Traffic Control-style link rules, a sidebar mini player and an Arc importer. It blocks ads and trackers by itself (EasyList and EasyPrivacy, on by default). Chrome Web Store extensions work, iCloud sync is optional, and AI (Codex, Claude Code or Apple on-device) is off by default. Builds are signed, notarized and auto-update, with an opt-in nightly channel, but it is Apple Silicon and macOS 15+ only, and a README labels it preview software. Favorites are shared by the Spaces of one profile, as in Arc. Netflix, Disney+, Max, Prime Video and Apple TV+ open in a WebKit tab with FairPlay (a fixed list, no published playback test) and Widevine playback was not verified. Touch ID passkeys work, but the signed app has no browser-passkey entitlement, so iCloud Keychain passkeys do not.
Built-in AI
AI optional
Off until you turn AI on in Settings and pick Codex, Claude Code or Apple's on-device model; then page chat, summaries, tab tidying, Skills, Boosts, Errands.
github.comBloat check
None found
No ads, wallet, feed, upsell or account (README: no browser account needed). Sparkle update checks send no system profile; no analytics SDK found in the source; nightly builds are opt-in.
github.comAds, crypto, paid upsells, news feeds, default-on telemetry, required accounts.
Organization
| Feature | Circa | Arc | Note |
|---|---|---|---|
| SidebarVertical sidebarTabs live in a vertical sidebar that is the main tab UI and can be hidden. | ✓ | ✓ | Tabs live in a sidebar; View > Show/Hide Sidebar (Cmd+S) hides it.github.com |
| SpacesSeveral workspaces per window, each with its own pinned and open tabs, switched by swipe or shortcut. | ✓ | ✓ | Spaces menu with Next/Previous (Opt+Cmd+arrows) and Ctrl+1-9; each Space has its own pinned tabs.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. | ✓ | ✓ | Each Space has a profile; Change Profile moves it to an existing or new one, so Spaces can share.github.com |
| FavoritesGlobal favoritesPinned icons at the top of the sidebar shared by every Space (Zen calls them Essentials). | ✓ | ✓ | Favorites belong to the profile and show in every Space on it, as in Arc; a new Space defaults to the active profile, so they are shared unless you pick another.github.com |
| Pinned TabsPinned tabs & foldersPer-space pinned tabs that act like bookmarks, with nested folders. | ✓ | ✓ | Pinned tabs are kept per Space and hold nested folders; New Folder is in the Tabs menu.github.com |
| Live foldersSidebar folders that fill and refresh themselves from an outside source, such as GitHub pull requests or an RSS feed. | ✓ | ✓ | GitHub pull-request folders fill themselves and refresh every 2 minutes, on app activation and on wake.github.com |
| ArchiveAuto-archive tabsUnpinned tabs close automatically after a set time and stay recoverable in an archive. | ✓ | ✓ | Today tabs auto-archive after a set delay (up to 30 days) and stay in an Archived Tabs view.github.com |
| Theme pickerSpace themesPer-space colour or gradient themes. | ✓ | ✓ | Each Space carries its own gradient theme with light and dark variants.github.com |
Browsing
| Feature | Circa | Arc | Note |
|---|---|---|---|
| Split ViewTwo or more tabs side by side in one window. | ✓ | ✓ | Up to four panes side by side (Ctrl+Shift+= adds a split).github.com |
| PeekLink previewOpen a link in an overlay without leaving the current page (Zen calls it Glance). | ✓ | ✓ | Shift-click, or a link leaving a pinned tab's site, opens a Peek overlay; both on by default.github.com |
| Little ArcMini windowA small, chrome-less window for links opened from other apps or a quick search. | ✓ | ✓ | Little Circa window is the default destination for links opened from other apps.github.com |
| Command barA ⌘T palette that searches tabs, history, bookmarks and browser commands. | ✓ | ✓ | Cmd+T/Cmd+L palette searches open tabs, pinned tabs, history, archived tabs and actions.github.com |
| Air Traffic ControlLink routingRules that send links from other apps to a chosen space or profile. | ✓ | ✓ | Ordered rules (URL contains, equals or host) send external links to a chosen Space.github.com |
| BoostsSite customizationPer-site custom CSS/JS, or zapping elements off a page. | ✓ | ✓ | Per-host Boosts with custom CSS, custom JavaScript and zapped elements.github.com |
| Auto PiPAuto picture-in-picturePlaying video pops out into picture-in-picture automatically when you switch tabs. | ✓ | ✓ | A video playing with sound on a page you have used enters picture-in-picture when you leave the tab; on by default, per-site toggle.github.com |
| Mini playerMedia still playing in a tab you left keeps play/pause controls in the sidebar. | ✓ | ✓ | A card at the sidebar bottom shows the site icon, previous, play/pause, next and close for media in a tab you left; it follows you across Spaces. Volume is not available yet.github.com |
| Tab SwitcherRecent-tab switcherCtrl+Tab jumps back to the tab you used last and cycles in recently used order. | ✓ | ✓ | Ctrl+Tab opens the Tab Switcher over a per-Space most-recently-used history; Ctrl+Shift+Tab goes backward.github.com |
| Super CopyClean link copyA shortcut (⌘⇧C) copies the page URL with tracking parameters removed. | ✓ | ✓ | Shift+Cmd+C Copy URL runs the copied address through a cleaner that drops utm_*, fbclid, gclid and some Amazon and Instagram ids.github.com |
| CaptureScreenshotsBuilt-in capture of a chosen area or element, and of the full page. | ✓ | ✓ | Shift+Cmd+2 Capture… drags a region to the clipboard; File > Capture Full Page; the Chromium engine declares both snapshot capabilities.github.com |
Compatibility & migration
| Feature | Circa | Arc | Note |
|---|---|---|---|
| Arc importImports Arc spaces, pinned tabs and folders. | ✓ | – | Imports Arc Spaces and tabs (passwords where available), including archived and Today tabs.github.com |
| Chrome extensionsInstalls extensions from the Chrome Web Store. | ✓ | ✓ | Installs from the Chrome Web Store on Chromium 158; README says compatibility is still evolving. Extensions do not run in WebKit tabs.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. | ◐ | ✓ | Fixed list (Netflix, Disney+, Max, Prime Video, Apple TV+) opens in WebKit with FairPlay; other Widevine requests are not rerouted. No playback test published; no Widevine in the bundle.github.com |
| PasskeysWebAuthn passkeys, Touch ID and the system/iCloud keychain. | ◐ | ✓ | Touch ID passkeys via Chromium's own authenticator (keychain group, since 0.70.1); security keys and phone QR work. No browser-passkey entitlement, so no iCloud Keychain passkeys.github.com |
| SyncSpaces, pinned tabs and settings sync across devices. | ✓ | ✓ | Optional iCloud sync of Spaces and tab organization; no Circa account needed.github.com |
| Mobile appiPhone, iPad or Android app that shares spaces with desktop. | ✕ | ◐ | No mobile app; the mobile folder only says one is planned for the future.github.com |
Extras
| Feature | Circa | Arc | Note |
|---|---|---|---|
| Built-in ad blockerAd and tracker blocking without installing an extension. | ✓ | ✓ | Built-in EasyList and EasyPrivacy blocking, on by default per profile; off in Settings > General, per-site allow, private windows too. Not applied in WebKit streaming tabs.github.com |
| Custom ShortcutsShortcut editorMost browser keyboard shortcuts can be remapped in Settings. | ✓ | ✓ | Settings > Shortcuts has a key recorder for the menu commands, with conflict checks and a search box.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 | Circa | Arc | Note |
|---|---|---|---|
| EaselsA shareable canvas of live page captures, notes and drawings. | ✕ | ◐ | No Easels or canvas: not in the feature table, and the source has no easel code.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. | ◐ | ✓ | Copy Link on several selected sidebar tabs gives text or Markdown, and bookmarks export writes HTML; no shareable Space or folder link.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 Gmail favorite or pinned tab opens an inbox card with unread mail; other Favorites show unread dots from title counts. A Calendar adapter exists, no UI uses it.github.com |
| Developer modeA developer view that turns on by itself for localhost: full URL, quick DevTools and dev tools in reach. | ✓ | ✓ | Ctrl+D toggles Developer Mode per host, on by default for localhost; it adds a toolbar with URL field, DevTools panels and capture.github.com |
Extension support
Which extension formats and stores run, beyond the Chrome Web Store row above.
| Feature | Circa | Arc | Note |
|---|---|---|---|
| Manifest V2 extensionsThe older extension format Chrome removed in 2025. Needed for full uBlock Origin and other extensions that block requests. | ? | ✕ | |
| Manifest V3 extensionsThe current extension format used by the Chrome Web Store (and supported by Firefox and Safari). | ✓ | ✓ | Chromium 158 extension host with Web Store install; MV3 DNR support not tested.github.com |
| Firefox add-onsAdd-ons from addons.mozilla.org or .xpi files install and run. | ✕ | ✕ | Chromium extensions only; README says Firefox extensions are not imported.github.com |
| Safari extensionsSafari web extensions (the App Store extension apps Safari uses) install and run. | ✕ | ✕ | Chromium extensions only; README says Safari extensions are not imported.github.com |