CaffeineTray

Ultra-light Windows tray app that prevents idle sleep. Left-click toggles. Right-click shows menu, Settings, and About. Dark/light follows system theme.

Features

• Prevents idle system sleep
• Optional display stay-on
• Single-instance guard
• Auto-start toggle (HKCU\Run)
• Theme-aware Settings + About
• Pure .NET 8 WinForms

Supported Windows

• Windows 11
• Windows 10 (1607+)
  Requires x64

Download

• Releases: single portable CaffeineTray.exe
  No installer. No extra files.

Run

Double-click CaffeineTray.exe.
Tray icon appears.
Left-click: toggle on/off.
Right-click: menu -> Settings..., About..., Exit.

Build from source

Only needed if you want to build; running the release EXE does not need .NET.

Prereqs

winget install Microsoft.DotNet.SDK.8           # Install .NET 8
winget install Microsoft.VisualStudioCode       # Install Visual Studio Code
code --install-extension ms-dotnettools.csharp  # Install C# vscode extension

Clone and build

git clone https://github.com/TheNolle/CaffeineTray.git
cd CaffeineTray
dotnet build

Publish portable single-file

dotnet publish -c Release -r win-x64 `
  -p:SelfContained=true -p:PublishSingleFile=true `
  -p:TrimMode=link -p:InvariantGlobalization=true
# output:
# .\bin\Release\net8.0-windows\win-x64\publish\CaffeineTray.exe

Usage

• ON blocks idle sleep.
• Also keep display awake blocks screen-off due to idle.
• Battery saver does not disable this. Manual sleep, lid-close, group policy, or critical battery can still suspend the PC.

Quick test (30 seconds)

powercfg /requests

Expect

SYSTEM:
  [PROCESS] CaffeineTray.exe
DISPLAY:                      # only if display option enabled
  [PROCESS] CaffeineTray.exe

Settings

• Start enabled: app starts ON
• Also keep display awake: blocks screen-off
• Run at Windows startup: toggles HKCU...\Run

Autostart (alt method)

Copy a shortcut to:

%APPDATA%\Microsoft\Windows\Start Menu\Programs\Startup

Theming

Follows Windows Apps theme:

• Light: standard WinForms palette
• Dark: dark content colors + DWM dark titlebar
  Auto-updates on theme change.

Single instance

A global mutex prevents multiple instances. Second launch exits immediately.

Power behavior details

• Uses SetThreadExecutionState(ES_CONTINUOUS | ES_SYSTEM_REQUIRED | ES_DISPLAY_REQUIRED*)
• Re-applies after resume and unlock
• Does not override:
  • Manual Sleep/Shutdown/Restart
  • Lid close policy
  • Critical battery actions
  • Admin/Group Policy timers
  • OEM power tools

Troubleshooting

• No tray icon: Explorer may have restarted. Unlock or re-login, or right-click -> Exit then relaunch. Icons are embedded; the EXE alone is sufficient.
• Double-click does nothing: an instance is already running in tray (single-instance guard).
• powercfg /requests shows nothing: ensure app is ON. Left-click the icon to toggle.

Development notes

Project targets net8.0-windows. Pure WinForms. Icons embedded as resources. No external deps.

Build scripts (optional defaults in csproj)

• Single-file self-contained publish:

dotnet publish -c Release -r win-x64 -p:SelfContained=true -p:PublishSingleFile=true -p:TrimMode=link -p:InvariantGlobalization=true

• Framework-dependent publish (tiny, needs .NET Desktop Runtime):

dotnet publish -c Release -r win-x64 -p:SelfContained=false -p:PublishSingleFile=false

Contributing

• Open issues: https://github.com/TheNolle/CaffeineTray/issues
• Send small, focused PRs. Keep it ultra-light. No new deps without discussion.
• Code style: minimal, documented where non-obvious, no bloat.

Privacy

• No telemetry
• No network calls
• collected

License

NFE-OSL v1.0

Credits

• Author: Nolly @ Nolly's Holding
• Versioning: 1.0.0 (Major.Minor.Hotfix)