A small Windows tray app that puts gentle fences on the edges between your monitors. It never changes your display layout.

_{Illustration of the behaviour, drawn from the app's own screenshots — not a screen recording.}

Download  ·   What it does  ·   Install  ·   Use  ·   Build  ·   FAQ  ·   Türkçe

The problem

With more than one monitor, the pointer slips onto the wrong screen all the time. A screen above your main one catches it whenever you aim for a tab or a title bar near the top edge. A side screen pulls it out of a borderless game in the middle of a fight. Windows lets you arrange your displays, but every shared edge is always open.

MouseFence leaves your Windows display layout exactly as it is and only decides what happens when the pointer reaches the edge between two screens.

What it does

Click the small gate between two screens in Settings → Displays and choose what that edge does. Each direction is set on its own: going up into the top screen can need a firm push while coming back down crosses freely.

Crosses freely A normal Windows monitor edge.

Needs a firm push Slow drift stops at the edge; one quick, deliberate move crosses.

Never crosses The pointer stays on its side.

Around the edges:

Keep pointer off Mark a screen the pointer must never enter; Windows keeps using it as normal.	Game mode Holds the pointer on whichever screen it is on, for windowed and borderless games.	Quick switches Upward passage, side protection and Pause, each with a global shortcut and a tray menu entry.
Crossing speed Tune how firm a firm push is, in pixels per second (default 3000).	Safety escapes After a layout change MouseFence keeps a way out of every screen, so the pointer is never sealed in.	Small and local Tray app, no installer, no network code; Light or Dark, English or Turkish, settings backup.

Install

1. Download MouseFence-win-x64.exe from the latest release.
2. Install the .NET 9 Desktop Runtime if you do not have it yet (the release file is small because it uses the shared runtime).
3. Put the file anywhere, for example %LOCALAPPDATA%\Programs\MouseFence\, and run it. It starts in the system tray and opens no window.
4. To start it with Windows, turn on Settings → General → Start with Windows.

Note

This README and its pictures describe the code on main (version 1.2.0, not released yet). The latest release, v1.1.1, has the same fences with an older look; 1.2.0 measures a firm push by the speed of the current move and adds a Crossing speed setting. To try it today, build from source.

Everyday use

1. Right-click the tray icon and choose Settings. Displays shows your screens as Windows arranges them.
2. Optionally name each screen, or tick Keep pointer off for a screen the pointer should never enter.
3. Click a small gate where two screens meet, pick Crosses freely, Needs a firm push or Never crosses, and select Save.

To cross a firm-push edge, move to the middle of the shared edge and push straight across in one quick motion. If it feels too stiff or too loose, change Advanced → Crossing speed (px/s) (default 3000; higher feels firmer).

Double-click the tray icon to open or close upward passage; right-click it for the menu.

Default shortcuts (change them in Settings → Shortcuts):

Action	Shortcut
Upward passage on or off	Ctrl + Alt + Up
Side protection on or off	Ctrl + Alt + Right
Game mode	Ctrl + Alt + G
Pause MouseFence	Ctrl + Alt + P

On a fresh install on a PC with Intel graphics, MouseFence adds Shift to the two arrow shortcuts, because the Intel driver uses Ctrl + Alt + arrow to rotate the screen.

Settings at a glance

Real captures of the app, drawn off-screen by its --screenshot-demo mode with a made-up three-screen layout (Main 2560 × 1440, Top above it, Laptop to the right). Each picture follows your GitHub light or dark theme.

Displays — your screens as Windows arranges them	Advanced — defaults, crossing speed, safety
Shortcuts — one global key for each switch	General — theme, language, start-up, backup

The interface is also available in Turkish (edge editor in Turkish).

How it works

flowchart LR
  A[Physical mouse move] --> B["Low-level mouse hook<br/>Platform/MouseGuard.cs"]
  B --> C["GuardCore<br/>pure, Win32-free decision"]
  D["Your edge rules<br/>Settings.cs"] --> E["BoundaryGraph<br/>rules → directed edges"]
  F["Live monitor rectangles<br/>Core/MonitorInfo.cs"] --> E
  E --> C
  C -->|pass| G[Pointer moves on]
  C -->|block| H["Held at the edge<br/>SetCursorPos"]

Loading

BoundaryGraph turns your saved rules into directed edges between the real screen rectangles. For each physical move, GuardCore decides whether it passes, stops at the edge, or lands on an allowed screen; a firm-push edge looks only at the speed of that single move. MouseFence reads screen positions and stable monitor identities and never calls the Windows functions that rearrange displays or change display modes.

Questions

The pointer still jumps between screens on its own. Turn off Windows Settings → System → Display → Multiple displays → Ease cursor movement between displays. That Windows 11 setting moves the pointer across edges for you and works against the fences.

Does it send anything over the network? No. MouseFence has no network code: no telemetry, no update check. It stores only settings.json (plain JSON; delete it to reset) and a small, size-limited error.log in %APPDATA%\MouseFence\.

It does nothing over a game or an administrator window. Windows does not let a normal app steer the pointer over exclusive-fullscreen games or over programs running as administrator. Windowed and borderless games work. Run MouseFence as administrator only if you need it over an elevated program.

The pointer cannot reach one of my screens. Open Displays: that screen is probably marked Keep pointer off, or the edge to it is Never crosses. Also check in the tray menu that MouseFence is not paused.

It will not start and says the settings file is invalid. MouseFence never overwrites a settings file it cannot read. Restore a backup from General → Restore from a file, or delete %APPDATA%\MouseFence\settings.json to start fresh. Details are in error.log.

How do I uninstall it? Turn off Start with Windows (it removes MouseFence's entry from your user's startup list), exit from the tray menu, then delete the exe and the %APPDATA%\MouseFence\ folder.

Build from source

You need Windows and the .NET 9 SDK.

git clone https://github.com/ydbilgin/MouseFence.git
cd MouseFence
dotnet run -c Release

A single-file exe that uses the shared .NET runtime, like the release (add --self-contained true -p:EnableCompressionInSingleFile=true for one that carries its own runtime):

dotnet publish -c Release -r win-x64 --self-contained false -p:PublishSingleFile=true

Tests. The test project is a console program, so use dotnet run, not dotnet test:

dotnet run --project tests/MouseFence.Tests.csproj -c Release

It covers edge rules, firm-push speed, side protection, safety escapes, settings migration, the English/Turkish texts, and the screenshot pictures.

Screenshots. The pictures above come from the app itself, drawn off-screen with made-up screens; nothing is read from your monitors:

dotnet build MouseFence.csproj -c Release -o build
build/MouseFence.exe --screenshot-demo docs/screenshots/displays-dark.png Dark 0 en
build/MouseFence.exe --screenshot-tray docs/screenshots/tray-menu-dark.png Dark en

The view number is 0 Displays, 1 Advanced, 2 Shortcuts, 3 General, -1 edge editor, and -2 Advanced with the physical-pixel controls open. The last argument is en or tr. The illustration at the top is rendered from docs/demo/scene.html; see docs/demo/README-demo.md. More notes for contributors are in docs/DEVELOPMENT.md.

Contributing, security, license

Contributions are welcome; CONTRIBUTING.md explains how to build, test and send a change. Please report security problems privately as described in SECURITY.md. MouseFence is released under the MIT license.

Türkçe

MouseFence, çok monitörlü Windows kurulumlarında fare imlecinin yanlış ekrana kaymasını önleyen küçük bir sistem tepsisi uygulamasıdır. Ekran düzeninize dokunmaz; yalnızca iki ekranın birleştiği kenarda ne olacağına karar verir: serbest geçiş, kararlı bir itişle geçiş ya da hiç geçmeme. Bir ekranı tamamen imleç dışı bırakabilir, oyun modunda imleci bulunduğu ekrana kilitleyebilirsiniz. Arayüz Türkçe de kullanılabilir.

• Kurulum: son sürümden MouseFence-win-x64.exe dosyasını indirin, gerekirse .NET 9 Desktop Runtime'ı kurun ve çalıştırın.
• Kullanım: tepsi simgesine sağ tıklayıp Ayarlar'ı açın, iki ekran arasındaki kapıya tıklayıp davranışı seçin ve kaydedin. Ayrıntılar: Everyday use, sorular: Questions.
• Ağ bağlantısı kurmaz; yalnızca ayarlarını ve küçük bir hata günlüğünü %APPDATA%\MouseFence\ içinde tutar.