Important: Chrome will be removing support for Chrome Apps on Windows, Mac, and Linux. Chrome OS will continue to support Chrome Apps. Additionally, Chrome and the Web Store will continue to support extensions on all platforms. Read the announcement and learn more about migrating your app.

Manifest - Icons

One or more icons that represent the extension, app, or theme. You should always provide a 128x128 icon; it's used during installation and by the Chrome Web Store. Extensions should also provide a 48x48 icon, which is used in the extensions management page (chrome://extensions). You can also specify a 16x16 icon to be used as the favicon for an extension's pages.

Icons should generally be in PNG format, because PNG has the best support for transparency. They can, however, be in any format supported by WebKit, including BMP, GIF, ICO, and JPEG. Here's an example of specifying the icons:

"icons": { "16": "icon16.png",
           "48": "icon48.png",
          "128": "icon128.png" },

You may provide icons of any other size you wish, and Chrome will attempt to use the best size where appropriate. For example, Windows often requires 32-pixel icons, and if the app includes a 32-pixel icon, Chrome will choose that instead of shrinking a 48-pixel icon down. However, you should ensure that all of your icons are square, or unexpected behavior may result.

If you upload your extension, app, or theme using the Chrome Developer Dashboard, you'll need to upload additional images, including at least one screenshot of your extension. For more information, see the Chrome Web Store developer documentation.