In Brackets, icons are used to:

• leverage globally understood visual concepts, or where icons usage is more conventional than text
• save space by using an easily understood symbol, where localization or text orientation is constrained direct the user visually and break down or differentiate elements (i.e. feature lists)
• enforce consistency within the application
• make the interface visually engaging.

• Use simple shapes that are not too detailed, use as less anchor points as possible
• Make sure it's flat i.e. without gradients, highlights, or shadows
• The corners are slightly rounded
• Use thinner lines rather than thicker lines
• Try to use SVG instead of PNG.

• A single icon is 24px × 24px with 3px padding so that the largest solid square you should have is 18px × 18px.
• For sprites use a 24x24 grid.

The icon should be #BBBBBB by default.

• Inactive/disabled state has an opacity of 0.4 set in CSS on the default icon
• Green (#91CC41) for "everything is okay right now"/success state
• Blue (#78B2F2) for on/active state
• Yellow (#E3B551) for warning state
• Red (#F74687) for error state.

###Icon Template

Download Extension Icon Template SVG

###CSS Example

#extension-name-icon {
    background-image: url(extension-name-sprite.svg);
}
 
#extension-name-icon.active {
    background-position: 0 -24px !important;
}

Ping @larz0 if you need help with your extension icon.