Zephium
Open-source Rust browser on the system WebKit/WebView2 engine, with a sidebar, Spaces and built-in agents.
Zephium is an open-source desktop browser written in Rust and Tauri, using the system web engine instead of bundling Chromium: WebKit on macOS and WebView2 on Windows. It has a vertical sidebar with spaces, profiles, pinned tabs, folders, split view and a global launcher, a native ad and tracker blocker, and installs extensions from the Chrome Web Store. It also has built-in notes, tasks and time tracking, an Ask Zephium page assistant and Work, an agent canvas that runs with your own model keys, a local model or paid Zephium AI. Its README pitches it as Safari's efficiency, Brave's protection and Arc's design, and the welcome flow imports from Arc.
60% Arc feature parity (yes = 1, partial = ½).
AI on by default
Ask Zephium sidebar and Work agents are on by default; AI can be switched off in Features. Needs your own key, a local model or a Zephium AI sign-in to answer.
github.comNot counted in Arc parity: some people want AI, some avoid it.
None found
No ads, wallet, feed or first-party telemetry; no account needed. Windows WebView2 sends required diagnostics to Microsoft. Credit prompts show only inside Zephium AI.
github.comAds, crypto, paid upsells, news feeds, default-on telemetry, required accounts.
Organization
| Feature | Zephium | Arc | Note |
|---|---|---|---|
| Vertical sidebarTabs live in a vertical sidebar that is the main tab UI and can be hidden. | ✓ | ✓ | Vertical sidebar is the only tab layout; Toggle Sidebar (⌘⇧S) hides it and it slides back from the edge.github.com |
| SpacesSeveral workspaces per window, each with its own pinned and open tabs, switched by swipe or shortcut. | ✓ | ✓ | Each space has its own Pinned and Today tabs; switch with ⌘⌥←/→, Ctrl+1–9 or a trackpad swipe.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. | ◐ | ✓ | Spaces live inside one profile (up to 24 each); no per-space profile picker, switch profile to see another set.github.com |
| Global favoritesPinned icons at the top of the sidebar shared by every Space (Zen calls them Essentials). | ◐ | ✓ | Essentials sit under the address field but belong to one space; no set shared by every space.github.com |
| Pinned tabs & foldersPer-space pinned tabs that act like bookmarks, with nested folders. | ✓ | ✓ | Per-space Pinned section with nested folders (tree depth up to 64).github.com |
| Auto-archive tabsUnpinned tabs close automatically after a set time and stay recoverable in an archive. | ◐ | ✓ | Idle Today tabs close into History after 12 h, 1 d or 7 d; off by default; no separate archive view.github.com |
| Space themesPer-space colour or gradient themes. | ✓ | ✓ | Each space can carry its own theme (preset or custom colours), icon and colour.github.com |
Browsing
| Feature | Zephium | Arc | Note |
|---|---|---|---|
| Split ViewTwo or more tabs side by side in one window. | ✓ | ✓ | Nested split tree, so any number of tabs side by side; drag a tab to a page edge or use Split View….github.com |
| Link previewOpen a link in an overlay without leaving the current page (Zen calls it Glance). | ✕ | ✓ | No link-preview overlay; the page area is native WebViews and chrome cannot paint over it.github.com |
| Mini windowA small, chrome-less window for links opened from other apps or a quick search. | ✕ | ✓ | A Little window kind is declared but only Main windows are ever created.github.com |
| Command barA ⌘T palette that searches tabs, history, bookmarks and browser commands. | ✓ | ✓ | Global launcher (⌘⇧Space) and address field search tabs, history, bookmarks, notes and commands.github.com |
| Link routingRules that send links from other apps to a chosen space or profile. | ✕ | ✓ | Links from other apps open as a new tab in the current space; only the tab position is a setting.github.com |
| Site customizationPer-site custom CSS/JS, or zapping elements off a page. | ✓ | ✓ | Pick-and-hide page elements saved per site; Ask Zephium can also save per-site CSS (AI needed).github.com |
| Auto picture-in-picturePlaying video pops out into picture-in-picture automatically when you switch tabs. | ✓ | ✓ | Video leaves the tab for PiP when you switch away, and returns on coming back; on by default.github.com |
Compatibility & migration
| Feature | Zephium | Arc | Note |
|---|---|---|---|
| Arc importImports Arc spaces, pinned tabs and folders. | ◐ | – | Reads Arc's sidebar file: favorites become Essentials, each space's pinned tabs a bookmark folder; no Spaces.github.com |
| Chrome extensionsInstalls extensions from the Chrome Web Store. | ✓ | ✓ | Add to Zephium on Chrome Web Store pages; WebKit lacks some APIs and 12 extensions run at once.github.com |
| DRM (Widevine)Netflix, Disney+, Spotify web and other DRM video/audio play. Chromium forks need a Google Widevine licence. | ? | ✓ | WebKit/WebView2 only; no Widevine or FairPlay code in the repo and no playback test run here. |
| PasskeysWebAuthn passkeys, Touch ID and the system/iCloud keychain. | ◐ | ✓ | Mac build lacks Apple's browser-passkey entitlement, so extensions only; Windows unchecked.github.com |
| SyncSpaces, pinned tabs and settings sync across devices. | ✕ | ✓ | No sync; data stays on the device and cloud sync is listed as post-release work.github.com |
| Mobile appiPhone, iPad or Android app that shares spaces with desktop. | ✕ | ◐ | Only a macOS (Apple Silicon) and a Windows x64 installer; Linux and Intel Macs are 'next'.github.com |
Extras
| Feature | Zephium | Arc | Note |
|---|---|---|---|
| Built-in ad blockerAd and tracker blocking without installing an extension. | ✓ | ✓ | Native blocker built on Brave's adblock-rust with EasyList/EasyPrivacy; on by default.github.com |
Extension support
Which extension formats and stores run, beyond the Chrome Web Store row above. Not counted in Arc parity.
| Feature | Zephium | Arc | Note |
|---|---|---|---|
| Manifest V2 extensionsThe older extension format Chrome removed in 2025. Needed for full uBlock Origin and other extensions that block requests. | ◐ | ✕ | macOS WebKit loads MV2 but has no blocking webRequest, so full uBlock Origin cannot work there.developer.apple.com |
| Manifest V3 extensionsThe current extension format used by the Chrome Web Store (and supported by Firefox and Safari). | ✓ | ✓ | Prepares MV3 packages for WebKit's extension engine; unsupported required APIs block the install.github.com |
| Firefox add-onsAdd-ons from addons.mozilla.org or .xpi files install and run. | ✕ | ✕ | Installs only from the Chrome Web Store; other extension stores are listed as later work.github.com |
| Safari extensionsSafari web extensions (the App Store extension apps Safari uses) install and run. | ✕ | ✕ | Installs only from the Chrome Web Store; no route for Safari web extension apps.github.com |