Density Toggle (Wear OS)

Shrinks the system display density on a Galaxy Watch so sideloaded phone apps fit the round screen, then restores it automatically when you leave the app. Built for the Galaxy Watch Ultra / Ultra 2 (One UI Watch / Wear OS), but works on any Wear OS watch where adb shell wm density works.

• No root. A one-time adb grant, then the watch is standalone forever.
• No account, no network, no telemetry. One permission, and the full source is right here so you can verify that.
• No Gradle. Plain javac → d8 → aapt → apksigner.

Why this exists: phone apps like YouTube, Uber, Proton, or Bitwarden are laid out for a large rectangular screen. At the watch's stock density their UI overflows the round display and controls fall outside the visible circle. Lowering display density makes those layouts fit.

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Install

You need a computer once to grant one permission. After that the watch never needs it again — the grant survives reboots and app updates.

1. Download DensityToggle.apk from the latest release.

2. Enable wireless debugging on the watch (Settings → Developer options).

3. Run the installer (it installs, grants the permission, and verifies it):

   # macOS / Linux
   bash install.sh <watch-ip>:<port>

   :: Windows
   install.bat <watch-ip>:<port>

   …or the three manual adb commands if you prefer — see INSTALL.md for the full walkthrough (pairing, finding the IP:port, troubleshooting).

Then on the watch: open Density Toggle, tap Auto, tap Choose apps, and pick the apps you want to auto-shrink.

What the installer actually does

No magic — four commands you could run yourself, all listed in INSTALL.md:

Step	Command	Why
Install	adb install -r DensityToggle.apk	the app itself
Grant	adb shell pm grant com.dt.toggle android.permission.WRITE_SECURE_SETTINGS	the one permission density changing needs — Android has no dialog for it, adb is the only way
Verify	adb shell dumpsys package com.dt.toggle | grep WRITE_SECURE_SETTINGS	confirms granted=true
Usage access	adb shell appops set com.dt.toggle android:get_usage_stats allow	lets the service read which app is in front from the system's usage ledger — accessibility events alone miss warm re-opens of running apps (YouTube especially). It reads app-switch timestamps, not content
Rotation lock (default; skip with --no-lock-rotation)	adb shell cmd window fixed-to-user-rotation enabled	pins the screen upright so shrunk apps stop rotating with your wrist; persists across reboots; undo with …disabled

Nothing else is changed, nothing runs on your computer afterwards, and the grants survive reboots — the watch never needs the computer again.

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Features

Automatic shrinking

An accessibility service watches which app is in front. When a chosen app appears it shrinks the display to that app's size; when you leave, it restores stock density. You enable the service from inside the app — no trip to Settings.

Per-app sizes

Every chosen app has its own density (a [−] value [+] stepper in Choose apps). A main-screen Auto size · default applies to apps without their own value. Hold a value to make it follow the default again; hold −/+ for bigger steps.

Works with secure apps

Password managers (Bitwarden, etc.) set FLAG_SECURE, which hides their screen from other apps. Density Toggle identifies the foreground app from window events, not screen content, so those apps shrink and restore correctly like any other.

Launch preemption

When you tap a watched app, the shrink is applied before the app finishes launching, so it opens straight into the right size instead of visibly rescaling mid-launch.

Rotation lock (installer default, opt-out)

A side effect of shrinking: phone apps switch to their tablet layouts, and tablet layouts rotate with the accelerometer — so apps flip sideways when you tilt your wrist. Android's auto-rotate setting can't stop this (apps that request sensor orientation bypass it), and the mode that can — the window manager's fixed-to-user-rotation — is guarded by a signature permission no sideloaded app can hold. So this is not an in-app toggle; it's one persistent adb command that the installer runs by default (skip with --no-lock-rotation; details in INSTALL.md):

adb shell cmd window fixed-to-user-rotation enabled    # undo: ...disabled

The system remembers it across reboots.

Reach

Round screens physically clip the corners of rectangular phone layouts, and no density setting can move a corner button into the visible circle. Reach is the workaround: a small translucent ⌕ button opens a list of the app's clickable controls that sit outside the circle — named by the app, or by position ("bottom-right control") when the app doesn't name them — and taps them for you (accessibility proxy-click; a control doesn't need to be visible to be clicked).

• Modes (main screen): off · shrunk apps (default) · all apps — "all apps" serves unshrunk third-party apps too, since corners are clipped at stock density as well. System apps never get the button.
• Per-app override: each app in Choose apps has a "⌕ Reach button" chip to hide the button just there.
• Transparency: adjustable 10–90% on the main screen (greyed out while Reach is off).
• Works for any app that exposes its UI tree; apps that hide it show "no hidden controls found".

Restore-to-stock escape hatch

A Restore to stock button appears on the main screen whenever the display is actually shrunk — one tap to get back to normal if anything ever sticks.

Diagnostics

A small grey line at the bottom reports which method changed the density, or the exact error if it failed. For deeper debugging the service logs every decision:

adb logcat -s DensityToggle

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How it works

Changing display density is gated by WRITE_SECURE_SETTINGS — the same gate adb shell wm density passes through. It is not a permission an app can grant itself or that Android shows a dialog for; it's handed over once via adb shell pm grant, and that grant persists across reboots. That single one-time command is the only reason a computer is needed at all.

WindowManagerService.setForcedDisplayDensityForUser() is hidden API, so the app reaches it by reflection. targetSdkVersion is pinned to 27 on purpose: hidden members marked max-target-o stay reachable for apps targeting API 27 or lower. See CLAUDE.md for the full mechanism, the fallback chain, and the invariants that are easy to break.

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Build from source

The release APK is ready to install; build it yourself only if you want to.

bash build-macos.sh          # or build-termux.sh on Android/Termux

Needs a JDK and Android SDK build-tools — not 34.0.0, whose dexer crashes on this project (the script skips it automatically). First build generates a local signing key; the resulting DensityToggle.apk is signed and installable.

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Compatibility

Tested on	Galaxy Watch Ultra (SM-L705U) & Ultra 2 (SM-L715U), Wear OS / Android 16–17
Min Wear OS	API 24
Requires	WRITE_SECURE_SETTINGS via one-time adb grant

Note on the Ultra / Ultra 2: both are 32-bit (armeabi-v7a). This app is pure Java so that doesn't affect it, but it does affect which other apps you can sideload — an arm64-only APK won't install. Prefer universal APKs.

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Troubleshooting

UI too small to tap. Tap Restore to stock in the app. If it's already too small for that, plug in and run adb shell wm density reset.

Installer says "no device / offline". The watch's wireless-debugging port changes every time it sleeps — re-read it on the watch and reconnect; clear stale entries with adb disconnect. Full details in INSTALL.md.

An app resizes oddly. Run adb logcat -s DensityToggle and open an issue with the output — it shows exactly what the service decided and why.

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License

MIT — see LICENSE. Provided as-is, no warranty. It changes a system display setting through a documented permission; the in-app Restore control and adb shell wm density reset undo anything it does.