Astro

A Chromium browser by Oxy: a sidebar instead of a toolbar, split view, and ads and trackers kept out.
Free and open source.

Status: in development, with no release yet. Astro builds and runs on macOS (Apple Silicon) today; Windows and Linux are the next targets.

What's in it

• Lose the toolbar. The address bar can live in the sidebar, so the page runs to the top of the window.
• Two pages, one window. Drag a tab onto the page: up to three panes, side by side or stacked.
• Refuses to leave the picture. Switch tabs mid-video and it floats along in the corner.
• Your extensions come along. The Chrome Web Store works as it does in Chrome.
• Ads and trackers stay out. uBlock Origin is built in, cookie banners included, and Google's background services are compiled out.
• Profiles, groups, themes, a command bar (⌘L for tabs, history, bookmarks and sums), clean links, tab sleeping, and import from Chrome, Safari, Firefox, Arc and more.

It's actually Chromium

Not WebKit, not Electron. The engine is Chromium 155 with a de-Googled patch series, and every web view is Chrome's own, so sites, extensions and DevTools behave as they do in Chrome. The interface on top is React Native with Expo.

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Build it yourself

A macOS browser that looks and feels like Dia: Chrome's own framework from our patched Chromium with our layer on top (AstroCore), an Expo + React Native macOS shell, and Metal shaders reconstructed from Dia's own New Tab effects.

apps/
  browser/            Expo + react-native-macos app (UI in src/, Xcode project in macos/)
packages/
  astrocore/             The engine: Chromium 155's framework with our layer (Chrome tabs hosted in our views), JS API in src/
  shell/              Native menu bar + shortcuts → JS, windows, SF Symbols, native primitives
  shaders/            Metal: New Tab effects + grained OKLab window backdrop
  import/             Import from other browsers (bookmarks, history, passwords, Arc spaces)
  core/               Pure TS: omnibox input → URL, suggestions, Dia-style breadcrumbs (tested)

Run it

Requires Xcode 26+, CocoaPods, Node 22.13+ (pinned in .nvmrc), pnpm 11.

pnpm install

The engine (Chrome's framework, built from our patched Chromium) has no prebuilt download yet, so build it from source once before the app: docs/engine-build.md › "Rebuilding". When releases publish engines, packages/astrocore/scripts/fetch-engine.sh downloads the one matching your checkout's engine/ and checks it against packages/astrocore/prebuilt-engines.tsv. Passkeys and saved cards need the team ID set in the Xcode project and won't work in a build signed by anyone else.

To change the engine itself (anything under engine/), build it from source: Chrome's framework from our patched Chromium tree in ~/chromium-build (Chromium 155.0.8059.84 with the patch series in engine/patches; docs/engine-build.md › "Rebuilding", then engine/chromium/apply.sh, engine/astrocore/apply.sh and autoninja -C out/Release_GN_arm64 chrome_framework; the first build takes about 2 hours). The app's build stages it from there when it exists.

pnpm pods

In one terminal, start Metro:

pnpm dev

In another, build and launch the Debug app (on its own data, ~/Library/Application Support/Astro Dev, or ASTRO_DATA_DIR):

pnpm macos

Other tasks: pnpm typecheck, pnpm test, pnpm shaders:check (compiles the embedded Metal offline), pnpm build (Release .app with a Hermes bytecode bundle in apps/browser/build/). Signed releases (DMG, Sparkle zip and appcast): scripts/release.sh <version>, see docs/releasing.md.

Shortcuts: ⌘T new tab, ⌘L command bar, ⌘W close, ⇧⌘T reopen, ⌘S sidebar, ⌘[ / ⌘] back/forward, ⌘R reload, ⌘1–⌘9 select tab, ⌃Tab cycle.

How Dia's New Tab light works

Dia 1.50 turns this light off along with its rebrand (a painted mark, a single-colour power-up band and a halo around the bar; docs/dia-spec.md › "1.50 Sunglow"), and so does Astro. The reconstruction left the tree with it: git show f2c0e251:packages/shaders/ios/AreaLightView.swift.

These findings come from disassembling the Metal libraries in Dia.app (v1.49.1) with xcrun metal-objdump. BoostBrowser_PowerUp.bundle/default.metallib contains breathingAreaLightFragment, which the Swift class NewTabPage.NewTabAreaLightView hosts. The reconstruction was AreaLightView.swift (above).

• The command bar is a light source. Dia models the bar as a rounded-rectangle area light floating lift points above the page. Each pixel receives the closed-form irradiance of that rectangle: the solid-angle formula, one atan term per corner, times 1/2π. Rounded corners subtract (1 − π/4) of each corner square. The result is a physically correct penumbra: a higher lift gives a softer, wider glow.
• Falloff is reshaped from inverse-square to (h/d)^falloff, where d is the distance to the emitter's rounded-rect surface rather than to its centre.
• Colour is Dia's brand spectrum (ProgressBarColor2…7 in its asset catalog): blue #0358F7, steel #5092C7, lavender #E1E1FE, yellow #FFD400, orange #FA3D1D and magenta #FD02F5. It is laid out as a wrapping, slightly diagonal gradient that scrolls every 20 s. IQ's 2D simplex noise warps the gradient under the bar, and the warp fades out into the penumbra.
• Dark mode treats the light as HDR emission and applies the Hable/Uncharted-2 filmic tonemap (white point 11.2), with alpha set to Rec.709 luminance. Light mode keeps the flat palette colour and uses the irradiance as opacity.
• Finishing: alpha fades over the top 50 pt and bottom 200 pt of the view, and ±3/255 triangular dither (Dave Hoskins' hash12) prevents banding in the long soft falloff.
• Animation: the shader itself only scrolls the colours. The lift-off intro and the slow "breathing" come from the CPU, which animates lift and intensity. Those curves live in Dia's Swift code, so the ones here (quartic ease-out over 1.1 s, ±7% intensity on a 5.5 s sine) are my approximation.

The window backdrop comes from ARC_WindowThemeUI.bundle (gradientFragment + renderFragment). Gradient stops are stored and mixed in OKLab, then converted to linear sRGB and gamma-encoded in the shader. A tiled grain texture is then multiply-blended on top. WindowBackdropView does the same with procedural grain.

Only math and colour values are reused. No Dia images, fonts or binaries are copied into this repo.

Architecture notes

• Why Expo SDK 54: react-native-macos tops out at 0.81, which pairs with Expo SDK 54 (whose ExpoAppDelegate / ExpoReactNativeFactory have macOS code paths).
• Legacy architecture. react-native-macos 0.81's Fabric support is experimental, so the app runs on the legacy architecture. One consequence: Expo's legacy view-manager adapter instantiates a module's first view class for every view it declares, so each native view has its own module.
• Metro, not expo start. Metro runs through the react-native-macos CLI. metro.config.js redirects react-native → react-native-macos for platform=macos, because defining our own resolveRequest replaces the redirect the CLI would install.
• No Reanimated. It has no macOS build for 0.81; animations use RN's Animated.
• Monorepo paths. pnpm is set to nodeLinker: hoisted because CocoaPods and Metro resolve react-native-macos by path. The Podfile rewrites REACT_NATIVE_PATH to the hoisted location and raises every pod's deployment target to 14.0, since Xcode 26+ rejects the 11.0 some Expo pods declare.
• Native subviews are sized in setFrameSize, not layout(). RN macOS assigns frames directly and never autoresizes subviews.
• Shaders are Metal source embedded in Swift and compiled at runtime (once per class, cached). This keeps the pods free of a metallib build phase.

Status

Feature parity with Dia is tracked row by row in docs/dia-feature-parity.md.

License

Astro as distributed is licensed under the GNU General Public License v3, because its engine is built with GPL-3.0 patches. Astro's own source files are under the Apache License 2.0. It builds on Chromium, carries a few of the Chromium Embedded Framework's patches to Chromium (BSD-3-Clause), and bundles uBlock Origin, each under its own license; see NOTICE. Every release links its source.