Optional. Defaults to false.

Use this to include a stylesheet in your popup that will make it 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 macOS.

The Firefox Style Guide 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.

Use this to specify an icon for the action.

It's recommended that you supply two icons here (19×19 pixels and 38×38 pixels), and specify them in an object with properties named "19" and "38", like this:

    "default_icon": {
      "19": "geo-19.png",
      "38": "geo-38.png"
    }

If you do this, then the browser will pick the right size icon for the screen's pixel density.

You can just supply a string here:

"default_icon": "geo.png"

If you do this, then the icon will be scaled to fit the toolbar, and may appear blurry.

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, don't use <script> with embedded code, because you'll get a Content Violation Policy error. Instead, <script> must use the src attribute to load a separate script file.

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 icon, displayed when the user moves their mouse over it.

This is a localizable property.

Hide the page action by default for pages whose URLs match any of the given match patterns.

Note that page actions are always hidden by default unless show_matches is given. Therefore, it only makes sense to include this property if show_matches is also given, and will override the patterns in show_matches.

For example, consider a value like:

"page_action": {
  "show_matches": ["https://*.mozilla.org/*"],
  "hide_matches": ["https://developer.mozilla.org/*"]
}

This shows the page action by default for all HTTPS URLs under the "mozilla.org" domain, except for pages under "developer.mozilla.org".

Show the page action by default for pages whose URLs match any of the given patterns.

See also hide_matches.

Optional. Defaults to true.

Controls whether or not the page action should appear in the location bar by default when the user installs the extension. This property is no longer supported since Firefox 89.