Browser Kernel

Manage the browser engines available to your apps. Open it from ⋮ → Browser Kernel.

Features

• Current WebView info — inspect the system WebView version on this device.
• Embedded engine — download, manage, and delete the optional GeckoView (Firefox) runtime. Shows download size and progress; the heavy native artifacts are fetched on first use.
• Change WebView provider — switch the system WebView provider (with developer-options steps guidance).
• Engine descriptions — reference info for Chrome, Edge, Brave, Firefox, and Via.

Notes

• Per-app engine selection happens in the Build APK dialog; this screen manages the engines themselves.
• ECH works on both engines; GeckoView is one option, not a requirement.

GeckoView (Firefox engine) feature support

GeckoView is a complete second engine independent of the system WebView, not a WebView skin: its network-layer capabilities are implemented natively by the engine, while a set of features that rely on WebView-only mechanisms (request interception, addJavascriptInterface, JS injection) are unavailable on GeckoView. Read this section before picking a kernel in the Build APK dialog.

Fully supported (native implementations, on par with the system WebView)

• ECH (encrypted SNI) — available on both engines; GeckoView implements it natively via TRR + its ECH prefs, the system WebView via the MITM bridge's Chromium upstream (auto-downloaded on first use, embedded in exported APKs)
• DoH, static / PAC / SOCKS5 proxy, anti-capture (force direct connection, ignore system proxies)
• UA modes and custom User-Agent, desktop mode
• JavaScript toggle, autoplay policy, viewport mode (fit screen / desktop), clear browsing data on launch, download toggle
• HTTP downloads, fullscreen video, file upload (incl. camera capture), automatic crash recovery
• Camera / microphone and geolocation permission policies (deny all / remember per host)
• mTLS client certificates, HTTP Basic / proxy auth dialogs
• JS dialogs (alert / confirm / prompt)
• Page-load error UI, back / forward history navigation, auto-refresh, find-in-page, console script execution
• Media session / lock-screen playback controls (native Gecko implementation)
• Page zoom — CSS zoom on the document root, the same script as the system WebView. Pinch zoom stays the engine's own
• Remote fetch and XHR stay on the engine, so a Cloudflare challenge can finish. The native bridge wraps those calls only on local pages
• Script-opened windows stay real child windows, so popup sign-in can post to window.opener and then close

Not available yet (choose the system WebView kernel if you need these)

• Ad blocking — neither network-rule filtering nor cosmetic hiding takes effect
• Userscripts (GM_* APIs) and Chrome MV3 extensions (incl. declarativeNetRequest / webRequest rules). The plugin list says this kernel can't run plugins, instead of saying none are enabled
• The full NativeBridge JS API — clipboard, notifications, vibration, printing, sharing, screen wake, orientation, Google sign-in, etc.; on GeckoView only the CORS-bypass / private-network httpRequest entry point is available
• JS-injection features — browser fingerprint disguise, device disguise, kernel disguise & flavors, page translation, audio unlock, clipboard / notification / orientation polyfills, Cloudflare compatibility helpers, custom injected scripts, popup blocking, scroll-position memory, image repair, hide-link-preview
• PWA offline (service-worker injection), static asset packs, encrypted asset loading — therefore HTML / front-end offline-package apps with resource encryption enabled must use the system WebView kernel
• blob / data: download interception
• The long-press menu (save image/video, copy link, etc.)
• Status-bar auto color sampling (follow page-top color; solid-color / theme modes are unaffected)
• Follow-system dark mode
• Cookie policy (GeckoView always accepts all cookies)
• Hosts mapping (domain → IP)
• Console message capture and eval result return (scripts do run, but the panel receives no messages or return values)
• New-window policy for ordinary links (same window, external browser, or block). A script-opened window is a real child window instead
• Proxy username / password authentication
• WebView state save / restore (session restore after process death)

Unsupported by design (trade-offs, not defects)

• TLS fingerprint spoofing (MITM bridge) and forced HTTP/3 (QUIC) — both ride the MITM bridge, which is a system-WebView-kernel feature; GeckoView natively presents a genuine Firefox TLS / JA3 fingerprint, which is the strongest "disguise" in itself, and the MITM bridge would terminate TLS and directly conflict with GeckoView's native ECH. On GeckoView, the target site sees a real Firefox.
• "Proceed anyway" on SSL certificate errors — GeckoView cannot ignore certificate errors, and editor-imported custom CAs are not trusted by GeckoView (only user CAs installed into the Android system, via the trust-user-certificates toggle).
• DOM storage / database cannot be disabled (always on in GeckoView).
• Floating-window mode always uses the system WebView regardless of the per-app engine choice.

Choosing an engine

• Apps that rely on ad blocking, userscripts, Chrome extensions, the NativeBridge API, or encrypted resource packaging → choose the system WebView.
• Apps that want a genuine Firefox fingerprint or Gecko engine behavior → choose GeckoView and accept the gaps listed above.
• ECH / SNI encryption works on both engines; if you also need TLS fingerprint spoofing or forced HTTP/3, choose the system WebView.
• Download the GeckoView runtime on this page first: the Build APK dialog will not offer the engine until it is installed, and host previews silently fall back to the system WebView when the runtime is missing.