Horizontal Scroll

A small Windows tray app: hold Mouse Back or Mouse Forward and roll the wheel to scroll sideways. The settings window follows the Fluent Design System: Mica background, light/dark mode and your accent color.

Features

• 🖱️ Hold to scroll sideways – Hold Mouse Back or Forward and roll the wheel.
• 👆 Clicks still work – A quick click without scrolling still goes back or forward as usual.
• 🔒 Toggle mode – Click once to lock horizontal scrolling on, click again to turn it off.
• 🎮 Game friendly – Turn off automatically in full-screen games, videos and F11 browsers.
• 🎛️ Make it yours – Pick the trigger button, scroll speed (0.5×–3.0×) and scroll direction.
• 🚀 Start with Windows – An optional toggle, so it's always ready.
• 📌 Lives in the tray – Closing the window keeps it running. Right-click the tray icon to pause it or exit.
• 🎨 Feels like Native App – Fluent Design with Mica, light/dark mode and your accent color, updated live.
• 🔔 Update check – See if a new version is out, right from the About section.

Limitations

• It doesn't work over windows of apps running as administrator unless Horizontal Scroll also runs as administrator. Windows blocks this.
• Apps without horizontal-scroll support won't scroll sideways.
• If mouse software (for example Logitech Options+) remaps Back/Forward to keystrokes, the app never sees the buttons.
• In hold mode, Back/Forward fires on button release, a moment later than usual.
• Single-file PyInstaller exes are sometimes flagged by antivirus heuristics. If that happens, build a one-folder version instead by moving a.binaries/a.datas into a COLLECT step in the spec.

Run

• Exe: download HorizontalScroll.exe from the Releases page, or build it yourself (see below). It's a single file, and Python isn't needed. Start it with --tray to start hidden.

• From source:

  python -m venv .venv
  .\.venv\Scripts\python -m pip install -r requirements.txt
  .\.venv\Scripts\pythonw main.py

  After that, you can also just double-click run.pyw to test your changes without building the exe.

Settings are saved to %APPDATA%\HorizontalScroll\config.json, and errors are logged to error.log in the same folder.

Build the exe

powershell -ExecutionPolicy Bypass -File build.ps1

The script creates .venv, installs the requirements plus PyInstaller, and writes dist\HorizontalScroll.exe (about 24 MB).

Tests

.\.venv\Scripts\python -m unittest discover -s tests -v

Layout

main.py              entry point: single instance, wires config, hook and UI
hscroll/engine.py    scroll/toggle/full-screen decisions (pure, unit-tested)
hscroll/hook.py      low-level mouse hook thread + SendInput injector thread
hscroll/winapi.py    ctypes bindings, input injection, full-screen detection
hscroll/config.py    settings (qfluentwidgets QConfig) and the Run-key autostart
hscroll/accent.py    Windows accent shades + watcher for accent changes
hscroll/window.py    Fluent settings window
hscroll/tray.py      tray icon and menu
hscroll/osd.py       toggle-mode on/off pill
hscroll/icons.py     icons drawn in code + .ico writer for the build

Disclaimer

This software is provided "as is", without warranty of any kind. Use it at your own risk; the author is not responsible for any damage or data loss resulting from its use.

Horizontal Scroll started as a personal project. It is not affiliated with or endorsed by Microsoft.

Claude Code was used in the development of this software.

License

GPL-3.0 © 2026 Ender Yang. Dependency information is in THIRD_PARTY_NOTICES.md.