Optional, defaulting to false.

Use this to include a stylesheet in your popup that will make its look consistent with the browser's UI and with other extensions that use the browser_style property. Although this key defaults to false, it's recommended that you include it and set it to true in order to make your popups consistent with the look of the rest of the browser user interface.

In Firefox, the stylesheet can be seen at chrome://browser/content/extension.css, or chrome://browser/content/extension-mac.css on OS X. When setting dimensions, be aware that this style sheet currently sets box-sizing: border-box (see box-sizing).

Browser styles describes the classes you can apply to elements in the popup in order to get particular styles.

The latest-download example extension uses browser_style in its popup.

Defines the part of the browser in which the button is initially placed. This is a string that may take one of four values:

• "navbar": the button is placed in the main browser toolbar, alongside the URL bar.
• "menupanel": the button is placed in a popup panel.
• "tabstrip": the button is placed in the toolbar that contains browser tabs.
• "personaltoolbar": the button is placed in the bookmarks toolbar.

This property is only supported in Firefox.

This property is optional, and defaults to "navbar".

Firefox remembers the default_area setting for an extension, even if that extension is uninstalled and subsequently reinstalled. To force the browser to acknowlege a new value for default_area, the id of the extension must be changed.

An extension can't change the location of the button after it has been installed, but the user may be able to move the button using the browser's built-in UI customization mechanism.

Use this to specify one or more icons for the browser action. The icon is shown in the browser toolbar by default.

Icons are specified as URLs relative to the manifest.json file itself.

You can specify a single icon file by supplying a string here:

"default_icon": "path/to/geo.svg"

To specify multiple icons in different sizes, specify an object here. The name of each property is the icon's height in pixels, and must be convertible to an integer. The value is the URL. For example:

    "default_icon": {
      "16": "path/to/geo-16.png",
      "32": "path/to/geo-32.png"
    }

You cannot specify multiple icons of the same sizes.

See Choosing icon sizes for more guidance on this.

The path to an HTML file containing the specification of the popup.

The HTML file may include CSS and JavaScript files using <link> and <script> elements, just like a normal web page. However, <script> must have src attribute to load a file. Don't use <script> with embedded code, because you'll get a confusing Content Violation Policy error.

Unlike a normal web page, JavaScript running in the popup can access all the WebExtension APIs (subject, of course, to the extension having the appropriate permissions).

This is a localizable property.

Tooltip for the button, displayed when the user moves their mouse over it. If the button is added to the browser's menu panel, this is also shown under the app icon.

This is a localizable property.

This property enables you to specify different icons for themes depending on whether Firefox detects that the theme uses dark or light text.

If this property is present, it's an array containing at least one ThemeIcons object. A ThemeIcons object contains three mandatory properties:

"dark"

A URL pointing to an icon. This icon displays when a theme using dark text is active (such as the Firefox Light theme, and the Default theme if no default_icon is specified).

"light"

A URL pointing to an icon. This icon displays when a theme using light text is active (such as the Firefox Dark theme).

"size"

The size of the two icons in pixels.

Icons are specified as URLs relative to the manifest.json file.

You should supply 16x16 and 32x32 (for retina display) ThemeIcons.