I want to change the notification icon of my application but don't know what is the size so as to make it properly displayed. Currently it is automatically resized and break my pixels! Please help!
It's 16x16. If you create a .ico file that supports 16, 32, 48 and 256 sizes, you're covered.
In fact the size of the icon will vary according to the system DPI.
WPF exposes the recommended pixel width and height of small icons with SystemParameters.SmallIconWidth and SystemParameters.SmallIconHeight. (WinForms exposes the equivalent SystemInformation.SmallIconSize - both just wrap around GetSystemMetrics and SM_CXSMICON/SM_CYSMICON.)
For XP it's 16 x 16
Outlook has an 16*16 pixels icon.
I believe it has always been 16x16, but at some point between 98 and XP (Maybe it was CE vs NT?) they learned to support full color and alpha transparency. If you can, try to include a 256 color palleted version in the ICO for safe mode if not older versions of Windows.
In ubuntu (unity) it seems to be 24x24 px.
Windows 7 has 16*16 pixels icons in system tray.
来源：https://stackoverflow.com/questions/3531232/what-is-the-size-of-the-icons-in-the-system-tray