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Holtdroid WebView is the test browser of Holtdroid, the self-hosted portal for Android test devices, but it doesn't need Holtdroid: install the APK on any device or emulator and use it on its own.

It opens a page in the system WebView (or GeckoView) and lets you change how that WebView is set up: full screen or with a toolbar, a fixed viewport size, strict or relaxed TLS, locked or unlocked features, a user agent, a proxy, user scripts. Remote debugging is on by default, so every page shows up in chrome://inspect and in Holtdroid's DevTools tab.

Features

• Presets on the start screen: Browse, Unlocked, Kiosk, App shell, Small phone, Desktop site, Fresh start and Proxy ship with the app; make your own, duplicate, reorder, pick a default.
• Display modes: standard (toolbar and system bars), immersive, edge to edge (the page under transparent bars, to test safe-area insets) and kiosk; toolbar on top or at the bottom; a floating handle for the controls when the toolbar is hidden; orientation lock; keep screen on.
• Viewport: frame the page at any size in CSS pixels, rotate it, scale it; freeze the page (timers, animations and rendering stop) and resume it.
• WebView settings: JavaScript, DOM storage, zoom, wide viewport, overview mode, text zoom, algorithmic darkening, autoplay, offline mode, image blocking, HTTP cache mode.
• Security: TLS errors strict / ask / ignore, mixed content, Safe Browsing, cookies and third-party cookies, site permissions ask / grant / deny, a host allowlist, popups, JavaScript dialogs, long press, file and content access, data wiped on start.
• Identity and network: desktop or custom user agent, a suffix, extra request headers, a proxy with a bypass list, user CA certificates trusted for mitmproxy and Charles.
• DevTools: remote debugging, an in-app console with a JavaScript prompt, Eruda bundled into the APK (works offline and under a strict CSP), a user script injected at document start.
• On-screen keyboard button for emulators with a hardware keyboard, where Android hides the on-screen one; it can switch show_ime_with_hard_keyboard on when granted WRITE_SECURE_SETTINGS.
• Engines: the system WebView (with the installed providers and the adb command that switches between them), GeckoView in the -gecko build, and Custom Tabs.
• Clear data: cache, cookies, storage, history or everything, from the panel or adb.
• adb control: every setting has a key; am start opens pages with overrides and am broadcast changes the open page live and answers with the result.
• Light, dark and system themes, Material You colours if you want them.

Install

Download an APK from Releases:

File	What
holtdroid-webview-<version>.apk	WebView and Custom Tabs, about 2 MB, any ABI
holtdroid-webview-gecko-<version>.apk	the same plus GeckoView for arm64-v8a, armeabi-v7a and x86_64, about 240 MB

They are two separate apps, Holtdroid WebView (io.github.holtdroid.webview) and Holtdroid WebView Gecko (io.github.holtdroid.webview.gecko), and can be installed side by side.

adb install -r holtdroid-webview-0.1.0.apk

Drive it from adb

P=io.github.holtdroid.webview   # or io.github.holtdroid.webview.gecko
A=io.github.holtdroid.webview

# open a page with a preset and overrides
adb shell am start -n $P/$A.MainActivity --es preset unlocked --es url https://example.com --es display kiosk

# change the open page live
adb shell am broadcast -a $A.CONTROL -p $P --es cmd resize --es size 360x640
adb shell am broadcast -a $A.CONTROL -p $P --es cmd freeze
adb shell am broadcast -a $A.CONTROL -p $P --es cmd clear --es what cookies
adb shell am broadcast -a $A.CONTROL -p $P --es cmd state

All commands and setting keys are in the documentation.

Build

The toolchain is JDK 21 (pinned in mise.toml) and the Android SDK with platform 37.2.

./gradlew testWebviewDebugUnitTest lintWebviewDebug lintGeckoDebug
./gradlew assembleWebviewDebug                     # app/build/outputs/apk/webview/debug
./gradlew assembleGeckoDebug -PgeckoAbi=x86_64     # GeckoView for one ABI (all three by default)
./gradlew assembleWebviewRelease -PappVersion=1.2.3

The build downloads Eruda from npm (version in app/build.gradle.kts, kept fresh by Renovate) and packs it into the APK's assets.

Release builds are signed when SIGNING_KEYSTORE, SIGNING_STORE_PASSWORD, SIGNING_KEY_ALIAS and SIGNING_KEY_PASSWORD are set, and with the debug key otherwise.

Releases

Every push to main runs .github/workflows/release.yml. It reads the Conventional Commits since the last tag: feat makes a minor release, fix and perf a patch, a breaking change a major one; other types release nothing. The workflow builds and signs the APKs, tags vX.Y.Z and publishes a GitHub release with the changelog.

Renovate keeps dependencies fresh (renovate.json): library updates land as fix(deps) commits, so a merged update ships as a patch release on its own. Minor and patch updates and GeckoView releases merge automatically once CI is green; other major updates wait for review.

License

Apache-2.0

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Caution

Fully AI-generated. Not a single line of this project was written or reviewed by a human: all of it was written by Claude through Claude Code. It's a Pandora's box, so use it at your own risk.